ui/events/gesture_detection/motion_event_buffer.cc - mojo - Git at Google

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 #include "ui/events/gesture_detection/motion_event_buffer.h"

 #include "base/trace_event/trace_event.h"
 #include "ui/events/gesture_detection/motion_event_generic.h"

 namespace ui {
 namespace {

 // Latency added during resampling. A few milliseconds doesn't hurt much but
 // reduces the impact of mispredicted touch positions.
 const int kResampleLatencyMs = 5;

 // Minimum time difference between consecutive samples before attempting to
 // resample.
 const int kResampleMinDeltaMs = 2;

 // Maximum time to predict forward from the last known state, to avoid
 // predicting too far into the future.  This time is further bounded by 50% of
 // the last time delta.
 const int kResampleMaxPredictionMs = 8;

 typedef ScopedVector<MotionEventGeneric> MotionEventVector;

 float Lerp(float a, float b, float alpha) {
   return a + alpha * (b - a);
 }

 bool CanAddSample(const MotionEvent& event0, const MotionEvent& event1) {
   DCHECK_EQ(event0.GetAction(), MotionEvent::ACTION_MOVE);
   if (event1.GetAction() != MotionEvent::ACTION_MOVE)
     return false;

   const size_t pointer_count = event0.GetPointerCount();
   if (pointer_count != event1.GetPointerCount())
     return false;

   for (size_t event0_i = 0; event0_i < pointer_count; ++event0_i) {
     const int id = event0.GetPointerId(event0_i);
     const int event1_i = event1.FindPointerIndexOfId(id);
     if (event1_i == -1)
       return false;
     if (event0.GetToolType(event0_i) != event1.GetToolType(event1_i))
       return false;
   }

   return true;
 }

 bool ShouldResampleTool(MotionEvent::ToolType tool) {
   return tool == MotionEvent::TOOL_TYPE_UNKNOWN ||
          tool == MotionEvent::TOOL_TYPE_FINGER;
 }

 size_t CountSamplesNoLaterThan(const MotionEventVector& batch,
                                base::TimeTicks time) {
   size_t count = 0;
   while (count < batch.size() && batch[count]->GetEventTime() <= time)
     ++count;
   return count;
 }

 MotionEventVector ConsumeSamplesNoLaterThan(MotionEventVector* batch,
                                             base::TimeTicks time) {
   DCHECK(batch);
   size_t count = CountSamplesNoLaterThan(*batch, time);
   DCHECK_GE(batch->size(), count);
   if (count == 0)
     return MotionEventVector();

   if (count == batch->size())
     return batch->Pass();

   // TODO(jdduke): Use a ScopedDeque to work around this mess.
   MotionEventVector unconsumed_batch;
   unconsumed_batch.insert(
       unconsumed_batch.begin(), batch->begin() + count, batch->end());
   batch->weak_erase(batch->begin() + count, batch->end());

   unconsumed_batch.swap(*batch);
   DCHECK_GE(unconsumed_batch.size(), 1U);
   return unconsumed_batch.Pass();
 }

 // Linearly interpolate the pointer position between two MotionEvent samples.
 // Only pointers of finger or unknown type will be resampled.
 PointerProperties ResamplePointer(const MotionEvent& event0,
                                   const MotionEvent& event1,
                                   size_t event0_pointer_index,
                                   size_t event1_pointer_index,
                                   float alpha) {
   DCHECK_EQ(event0.GetPointerId(event0_pointer_index),
             event1.GetPointerId(event1_pointer_index));
   // If the tool should not be resampled, use the latest event in the valid
   // horizon (i.e., the event no later than the time interpolated by alpha).
   if (!ShouldResampleTool(event0.GetToolType(event0_pointer_index))) {
     if (alpha > 1)
       return PointerProperties(event1, event1_pointer_index);
     else
       return PointerProperties(event0, event0_pointer_index);
   }

   PointerProperties p(event0, event0_pointer_index);
   p.x = Lerp(p.x, event1.GetX(event1_pointer_index), alpha);
   p.y = Lerp(p.y, event1.GetY(event1_pointer_index), alpha);
   p.raw_x = Lerp(p.raw_x, event1.GetRawX(event1_pointer_index), alpha);
   p.raw_y = Lerp(p.raw_y, event1.GetRawY(event1_pointer_index), alpha);
   return p;
 }

 // Linearly interpolate the pointers between two event samples using the
 // provided |resample_time|.
 scoped_ptr<MotionEventGeneric> ResampleMotionEvent(
     const MotionEvent& event0,
     const MotionEvent& event1,
     base::TimeTicks resample_time) {
   DCHECK_EQ(MotionEvent::ACTION_MOVE, event0.GetAction());
   DCHECK_EQ(event0.GetPointerCount(), event1.GetPointerCount());

   const base::TimeTicks time0 = event0.GetEventTime();
   const base::TimeTicks time1 = event1.GetEventTime();
   DCHECK(time0 < time1);
   DCHECK(time0 <= resample_time);

   const float alpha = (resample_time - time0).InMillisecondsF() /
                       (time1 - time0).InMillisecondsF();

   scoped_ptr<MotionEventGeneric> event;
   const size_t pointer_count = event0.GetPointerCount();
   DCHECK_EQ(pointer_count, event1.GetPointerCount());
   for (size_t event0_i = 0; event0_i < pointer_count; ++event0_i) {
     int event1_i = event1.FindPointerIndexOfId(event0.GetPointerId(event0_i));
     DCHECK_NE(event1_i, -1);
     PointerProperties pointer = ResamplePointer(
         event0, event1, event0_i, static_cast<size_t>(event1_i), alpha);

     if (event0_i == 0) {
       event.reset(new MotionEventGeneric(
           MotionEvent::ACTION_MOVE, resample_time, pointer));
     } else {
       event->PushPointer(pointer);
     }
   }

   DCHECK(event);
   event->set_button_state(event0.GetButtonState());
   return event.Pass();
 }

 // Synthesize a compound MotionEventGeneric event from a sequence of events.
 // Events must be in non-decreasing (time) order.
 scoped_ptr<MotionEventGeneric> ConsumeSamples(MotionEventVector events) {
   DCHECK(!events.empty());
   scoped_ptr<MotionEventGeneric> event(events.back());
   for (size_t i = 0; i + 1 < events.size(); ++i)
     event->PushHistoricalEvent(scoped_ptr<MotionEvent>(events[i]));
   events.weak_clear();
   return event.Pass();
 }

 // Consume a series of event samples, attempting to synthesize a new, synthetic
 // event if the samples and sample time meet certain interpolation/extrapolation
 // conditions. If such conditions are met, the provided samples will be added
 // to the synthetic event's history, otherwise, the samples will be used to
 // generate a basic, compound event.
 // TODO(jdduke): Revisit resampling to handle cases where alternating frames
 // are resampled or resampling is otherwise inconsistent, e.g., a 90hz input
 // and 60hz frame signal could phase-align such that even frames yield an
 // extrapolated event and odd frames are not resampled, crbug.com/399381.
 scoped_ptr<MotionEventGeneric> ConsumeSamplesAndTryResampling(
     base::TimeTicks resample_time,
     MotionEventVector events,
     const MotionEvent* next) {
   const ui::MotionEvent* event0 = nullptr;
   const ui::MotionEvent* event1 = nullptr;
   if (next) {
     DCHECK(resample_time < next->GetEventTime());
     // Interpolate between current sample and future sample.
     event0 = events.back();
     event1 = next;
   } else if (events.size() >= 2) {
     // Extrapolate future sample using current sample and past sample.
     event0 = events[events.size() - 2];
     event1 = events[events.size() - 1];

     const base::TimeTicks time1 = event1->GetEventTime();
     base::TimeTicks max_predict =
         time1 +
         std::min((event1->GetEventTime() - event0->GetEventTime()) / 2,
                  base::TimeDelta::FromMilliseconds(kResampleMaxPredictionMs));
     if (resample_time > max_predict) {
       TRACE_EVENT_INSTANT2("input",
                            "MotionEventBuffer::TryResample prediction adjust",
                            TRACE_EVENT_SCOPE_THREAD,
                            "original(ms)",
                            (resample_time - time1).InMilliseconds(),
                            "adjusted(ms)",
                            (max_predict - time1).InMilliseconds());
       resample_time = max_predict;
     }
   } else {
     TRACE_EVENT_INSTANT0("input",
                          "MotionEventBuffer::TryResample insufficient data",
                          TRACE_EVENT_SCOPE_THREAD);
     return ConsumeSamples(events.Pass());
   }

   DCHECK(event0);
   DCHECK(event1);
   const base::TimeTicks time0 = event0->GetEventTime();
   const base::TimeTicks time1 = event1->GetEventTime();
   base::TimeDelta delta = time1 - time0;
   if (delta < base::TimeDelta::FromMilliseconds(kResampleMinDeltaMs)) {
     TRACE_EVENT_INSTANT1("input",
                          "MotionEventBuffer::TryResample failure",
                          TRACE_EVENT_SCOPE_THREAD,
                          "event_delta_too_small(ms)",
                          delta.InMilliseconds());
     return ConsumeSamples(events.Pass());
   }

   scoped_ptr<MotionEventGeneric> resampled_event =
       ResampleMotionEvent(*event0, *event1, resample_time);
   for (size_t i = 0; i < events.size(); ++i)
     resampled_event->PushHistoricalEvent(scoped_ptr<MotionEvent>(events[i]));
   events.weak_clear();
   return resampled_event.Pass();
 }

 }  // namespace

 MotionEventBuffer::MotionEventBuffer(MotionEventBufferClient* client,
                                      bool enable_resampling)
     : client_(client), resample_(enable_resampling) {
 }

 MotionEventBuffer::~MotionEventBuffer() {
 }

 void MotionEventBuffer::OnMotionEvent(const MotionEvent& event) {
   DCHECK_EQ(0U, event.GetHistorySize());
   if (event.GetAction() != MotionEvent::ACTION_MOVE) {
     last_extrapolated_event_time_ = base::TimeTicks();
     if (!buffered_events_.empty())
       FlushWithoutResampling(buffered_events_.Pass());
     client_->ForwardMotionEvent(event);
     return;
   }

   // Guard against events that are *older* than the last one that may have been
   // artificially synthesized.
   if (!last_extrapolated_event_time_.is_null()) {
     DCHECK(buffered_events_.empty());
     if (event.GetEventTime() < last_extrapolated_event_time_)
       return;
     last_extrapolated_event_time_ = base::TimeTicks();
   }

   scoped_ptr<MotionEventGeneric> clone = MotionEventGeneric::CloneEvent(event);
   if (buffered_events_.empty()) {
     buffered_events_.push_back(clone.Pass());
     client_->SetNeedsFlush();
     return;
   }

   if (CanAddSample(*buffered_events_.front(), *clone)) {
     DCHECK(buffered_events_.back()->GetEventTime() <= clone->GetEventTime());
   } else {
     FlushWithoutResampling(buffered_events_.Pass());
   }

   buffered_events_.push_back(clone.Pass());
   // No need to request another flush as the first event will have requested it.
 }

 void MotionEventBuffer::Flush(base::TimeTicks frame_time) {
   if (buffered_events_.empty())
     return;

   // Shifting the sample time back slightly minimizes the potential for
   // misprediction when extrapolating events.
   if (resample_)
     frame_time -= base::TimeDelta::FromMilliseconds(kResampleLatencyMs);

   // TODO(jdduke): Use a persistent MotionEventVector vector for temporary
   // storage.
   MotionEventVector events(
       ConsumeSamplesNoLaterThan(&buffered_events_, frame_time));
   if (events.empty()) {
     DCHECK(!buffered_events_.empty());
     client_->SetNeedsFlush();
     return;
   }

   if (!resample_ || (events.size() == 1 && buffered_events_.empty())) {
     FlushWithoutResampling(events.Pass());
     if (!buffered_events_.empty())
       client_->SetNeedsFlush();
     return;
   }

   FlushWithResampling(events.Pass(), frame_time);
 }

 void MotionEventBuffer::FlushWithResampling(MotionEventVector events,
                                             base::TimeTicks resample_time) {
   DCHECK(!events.empty());
   base::TimeTicks original_event_time = events.back()->GetEventTime();
   const MotionEvent* next_event =
       !buffered_events_.empty() ? buffered_events_.front() : nullptr;

   scoped_ptr<MotionEventGeneric> resampled_event =
       ConsumeSamplesAndTryResampling(resample_time, events.Pass(), next_event);
   DCHECK(resampled_event);

   // Log the extrapolated event time, guarding against subsequently queued
   // events that might have an earlier timestamp.
   if (!next_event && resampled_event->GetEventTime() > original_event_time) {
     last_extrapolated_event_time_ = resampled_event->GetEventTime();
   } else {
     last_extrapolated_event_time_ = base::TimeTicks();
   }

   client_->ForwardMotionEvent(*resampled_event);
   if (!buffered_events_.empty())
     client_->SetNeedsFlush();
 }

 void MotionEventBuffer::FlushWithoutResampling(MotionEventVector events) {
   last_extrapolated_event_time_ = base::TimeTicks();
   if (events.empty())
     return;

   client_->ForwardMotionEvent(*ConsumeSamples(events.Pass()));
 }

 }  // namespace ui
	// Copyright 2014 The Chromium Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	#include "ui/events/gesture_detection/motion_event_buffer.h"

	#include "base/trace_event/trace_event.h"
	#include "ui/events/gesture_detection/motion_event_generic.h"

	namespace ui {
	namespace {

	// Latency added during resampling. A few milliseconds doesn't hurt much but
	// reduces the impact of mispredicted touch positions.
	const int kResampleLatencyMs = 5;

	// Minimum time difference between consecutive samples before attempting to
	// resample.
	const int kResampleMinDeltaMs = 2;

	// Maximum time to predict forward from the last known state, to avoid
	// predicting too far into the future. This time is further bounded by 50% of
	// the last time delta.
	const int kResampleMaxPredictionMs = 8;

	typedef ScopedVector<MotionEventGeneric> MotionEventVector;

	float Lerp(float a, float b, float alpha) {
	return a + alpha * (b - a);
	}

	bool CanAddSample(const MotionEvent& event0, const MotionEvent& event1) {
	DCHECK_EQ(event0.GetAction(), MotionEvent::ACTION_MOVE);
	if (event1.GetAction() != MotionEvent::ACTION_MOVE)
	return false;

	const size_t pointer_count = event0.GetPointerCount();
	if (pointer_count != event1.GetPointerCount())
	return false;

	for (size_t event0_i = 0; event0_i < pointer_count; ++event0_i) {
	const int id = event0.GetPointerId(event0_i);
	const int event1_i = event1.FindPointerIndexOfId(id);
	if (event1_i == -1)
	return false;
	if (event0.GetToolType(event0_i) != event1.GetToolType(event1_i))
	return false;
	}

	return true;
	}

	bool ShouldResampleTool(MotionEvent::ToolType tool) {
	return tool == MotionEvent::TOOL_TYPE_UNKNOWN \|\|
	tool == MotionEvent::TOOL_TYPE_FINGER;
	}

	size_t CountSamplesNoLaterThan(const MotionEventVector& batch,
	base::TimeTicks time) {
	size_t count = 0;
	while (count < batch.size() && batch[count]->GetEventTime() <= time)
	++count;
	return count;
	}

	MotionEventVector ConsumeSamplesNoLaterThan(MotionEventVector* batch,
	base::TimeTicks time) {
	DCHECK(batch);
	size_t count = CountSamplesNoLaterThan(*batch, time);
	DCHECK_GE(batch->size(), count);
	if (count == 0)
	return MotionEventVector();

	if (count == batch->size())
	return batch->Pass();

	// TODO(jdduke): Use a ScopedDeque to work around this mess.
	MotionEventVector unconsumed_batch;
	unconsumed_batch.insert(
	unconsumed_batch.begin(), batch->begin() + count, batch->end());
	batch->weak_erase(batch->begin() + count, batch->end());

	unconsumed_batch.swap(*batch);
	DCHECK_GE(unconsumed_batch.size(), 1U);
	return unconsumed_batch.Pass();
	}

	// Linearly interpolate the pointer position between two MotionEvent samples.
	// Only pointers of finger or unknown type will be resampled.
	PointerProperties ResamplePointer(const MotionEvent& event0,
	const MotionEvent& event1,
	size_t event0_pointer_index,
	size_t event1_pointer_index,
	float alpha) {
	DCHECK_EQ(event0.GetPointerId(event0_pointer_index),
	event1.GetPointerId(event1_pointer_index));
	// If the tool should not be resampled, use the latest event in the valid
	// horizon (i.e., the event no later than the time interpolated by alpha).
	if (!ShouldResampleTool(event0.GetToolType(event0_pointer_index))) {
	if (alpha > 1)
	return PointerProperties(event1, event1_pointer_index);
	else
	return PointerProperties(event0, event0_pointer_index);
	}

	PointerProperties p(event0, event0_pointer_index);
	p.x = Lerp(p.x, event1.GetX(event1_pointer_index), alpha);
	p.y = Lerp(p.y, event1.GetY(event1_pointer_index), alpha);
	p.raw_x = Lerp(p.raw_x, event1.GetRawX(event1_pointer_index), alpha);
	p.raw_y = Lerp(p.raw_y, event1.GetRawY(event1_pointer_index), alpha);
	return p;
	}

	// Linearly interpolate the pointers between two event samples using the
	// provided \|resample_time\|.
	scoped_ptr<MotionEventGeneric> ResampleMotionEvent(
	const MotionEvent& event0,
	const MotionEvent& event1,
	base::TimeTicks resample_time) {
	DCHECK_EQ(MotionEvent::ACTION_MOVE, event0.GetAction());
	DCHECK_EQ(event0.GetPointerCount(), event1.GetPointerCount());

	const base::TimeTicks time0 = event0.GetEventTime();
	const base::TimeTicks time1 = event1.GetEventTime();
	DCHECK(time0 < time1);
	DCHECK(time0 <= resample_time);

	const float alpha = (resample_time - time0).InMillisecondsF() /
	(time1 - time0).InMillisecondsF();

	scoped_ptr<MotionEventGeneric> event;
	const size_t pointer_count = event0.GetPointerCount();
	DCHECK_EQ(pointer_count, event1.GetPointerCount());
	for (size_t event0_i = 0; event0_i < pointer_count; ++event0_i) {
	int event1_i = event1.FindPointerIndexOfId(event0.GetPointerId(event0_i));
	DCHECK_NE(event1_i, -1);
	PointerProperties pointer = ResamplePointer(
	event0, event1, event0_i, static_cast<size_t>(event1_i), alpha);

	if (event0_i == 0) {
	event.reset(new MotionEventGeneric(
	MotionEvent::ACTION_MOVE, resample_time, pointer));
	} else {
	event->PushPointer(pointer);
	}
	}

	DCHECK(event);
	event->set_button_state(event0.GetButtonState());
	return event.Pass();
	}

	// Synthesize a compound MotionEventGeneric event from a sequence of events.
	// Events must be in non-decreasing (time) order.
	scoped_ptr<MotionEventGeneric> ConsumeSamples(MotionEventVector events) {
	DCHECK(!events.empty());
	scoped_ptr<MotionEventGeneric> event(events.back());
	for (size_t i = 0; i + 1 < events.size(); ++i)
	event->PushHistoricalEvent(scoped_ptr<MotionEvent>(events[i]));
	events.weak_clear();
	return event.Pass();
	}

	// Consume a series of event samples, attempting to synthesize a new, synthetic
	// event if the samples and sample time meet certain interpolation/extrapolation
	// conditions. If such conditions are met, the provided samples will be added
	// to the synthetic event's history, otherwise, the samples will be used to
	// generate a basic, compound event.
	// TODO(jdduke): Revisit resampling to handle cases where alternating frames
	// are resampled or resampling is otherwise inconsistent, e.g., a 90hz input
	// and 60hz frame signal could phase-align such that even frames yield an
	// extrapolated event and odd frames are not resampled, crbug.com/399381.
	scoped_ptr<MotionEventGeneric> ConsumeSamplesAndTryResampling(
	base::TimeTicks resample_time,
	MotionEventVector events,
	const MotionEvent* next) {
	const ui::MotionEvent* event0 = nullptr;
	const ui::MotionEvent* event1 = nullptr;
	if (next) {
	DCHECK(resample_time < next->GetEventTime());
	// Interpolate between current sample and future sample.
	event0 = events.back();
	event1 = next;
	} else if (events.size() >= 2) {
	// Extrapolate future sample using current sample and past sample.
	event0 = events[events.size() - 2];
	event1 = events[events.size() - 1];

	const base::TimeTicks time1 = event1->GetEventTime();
	base::TimeTicks max_predict =
	time1 +
	std::min((event1->GetEventTime() - event0->GetEventTime()) / 2,
	base::TimeDelta::FromMilliseconds(kResampleMaxPredictionMs));
	if (resample_time > max_predict) {
	TRACE_EVENT_INSTANT2("input",
	"MotionEventBuffer::TryResample prediction adjust",
	TRACE_EVENT_SCOPE_THREAD,
	"original(ms)",
	(resample_time - time1).InMilliseconds(),
	"adjusted(ms)",
	(max_predict - time1).InMilliseconds());
	resample_time = max_predict;
	}
	} else {
	TRACE_EVENT_INSTANT0("input",
	"MotionEventBuffer::TryResample insufficient data",
	TRACE_EVENT_SCOPE_THREAD);
	return ConsumeSamples(events.Pass());
	}

	DCHECK(event0);
	DCHECK(event1);
	const base::TimeTicks time0 = event0->GetEventTime();
	const base::TimeTicks time1 = event1->GetEventTime();
	base::TimeDelta delta = time1 - time0;
	if (delta < base::TimeDelta::FromMilliseconds(kResampleMinDeltaMs)) {
	TRACE_EVENT_INSTANT1("input",
	"MotionEventBuffer::TryResample failure",
	TRACE_EVENT_SCOPE_THREAD,
	"event_delta_too_small(ms)",
	delta.InMilliseconds());
	return ConsumeSamples(events.Pass());
	}

	scoped_ptr<MotionEventGeneric> resampled_event =
	ResampleMotionEvent(event0, event1, resample_time);
	for (size_t i = 0; i < events.size(); ++i)
	resampled_event->PushHistoricalEvent(scoped_ptr<MotionEvent>(events[i]));
	events.weak_clear();
	return resampled_event.Pass();
	}

	} // namespace

	MotionEventBuffer::MotionEventBuffer(MotionEventBufferClient* client,
	bool enable_resampling)
	: client_(client), resample_(enable_resampling) {
	}

	MotionEventBuffer::~MotionEventBuffer() {
	}

	void MotionEventBuffer::OnMotionEvent(const MotionEvent& event) {
	DCHECK_EQ(0U, event.GetHistorySize());
	if (event.GetAction() != MotionEvent::ACTION_MOVE) {
	last_extrapolated_event_time_ = base::TimeTicks();
	if (!buffered_events_.empty())
	FlushWithoutResampling(buffered_events_.Pass());
	client_->ForwardMotionEvent(event);
	return;
	}

	// Guard against events that are older than the last one that may have been
	// artificially synthesized.
	if (!last_extrapolated_event_time_.is_null()) {
	DCHECK(buffered_events_.empty());
	if (event.GetEventTime() < last_extrapolated_event_time_)
	return;
	last_extrapolated_event_time_ = base::TimeTicks();
	}

	scoped_ptr<MotionEventGeneric> clone = MotionEventGeneric::CloneEvent(event);
	if (buffered_events_.empty()) {
	buffered_events_.push_back(clone.Pass());
	client_->SetNeedsFlush();
	return;
	}

	if (CanAddSample(buffered_events_.front(), clone)) {
	DCHECK(buffered_events_.back()->GetEventTime() <= clone->GetEventTime());
	} else {
	FlushWithoutResampling(buffered_events_.Pass());
	}

	buffered_events_.push_back(clone.Pass());
	// No need to request another flush as the first event will have requested it.
	}

	void MotionEventBuffer::Flush(base::TimeTicks frame_time) {
	if (buffered_events_.empty())
	return;

	// Shifting the sample time back slightly minimizes the potential for
	// misprediction when extrapolating events.
	if (resample_)
	frame_time -= base::TimeDelta::FromMilliseconds(kResampleLatencyMs);

	// TODO(jdduke): Use a persistent MotionEventVector vector for temporary
	// storage.
	MotionEventVector events(
	ConsumeSamplesNoLaterThan(&buffered_events_, frame_time));
	if (events.empty()) {
	DCHECK(!buffered_events_.empty());
	client_->SetNeedsFlush();
	return;
	}

	if (!resample_ \|\| (events.size() == 1 && buffered_events_.empty())) {
	FlushWithoutResampling(events.Pass());
	if (!buffered_events_.empty())
	client_->SetNeedsFlush();
	return;
	}

	FlushWithResampling(events.Pass(), frame_time);
	}

	void MotionEventBuffer::FlushWithResampling(MotionEventVector events,
	base::TimeTicks resample_time) {
	DCHECK(!events.empty());
	base::TimeTicks original_event_time = events.back()->GetEventTime();
	const MotionEvent* next_event =
	!buffered_events_.empty() ? buffered_events_.front() : nullptr;

	scoped_ptr<MotionEventGeneric> resampled_event =
	ConsumeSamplesAndTryResampling(resample_time, events.Pass(), next_event);
	DCHECK(resampled_event);

	// Log the extrapolated event time, guarding against subsequently queued
	// events that might have an earlier timestamp.
	if (!next_event && resampled_event->GetEventTime() > original_event_time) {
	last_extrapolated_event_time_ = resampled_event->GetEventTime();
	} else {
	last_extrapolated_event_time_ = base::TimeTicks();
	}

	client_->ForwardMotionEvent(*resampled_event);
	if (!buffered_events_.empty())
	client_->SetNeedsFlush();
	}

	void MotionEventBuffer::FlushWithoutResampling(MotionEventVector events) {
	last_extrapolated_event_time_ = base::TimeTicks();
	if (events.empty())
	return;

	client_->ForwardMotionEvent(*ConsumeSamples(events.Pass()));
	}

	} // namespace ui