Sync ui/events to chromium @ https://crrev.com/336230

ui/gfx/screen_aura.cc -> ui/gfx/screen_stub.cc

Carrying forward previous rename of:

 gesture_provider_aura -> gesture_provider_impl
 motion_event_aura -> motion_event_impl

Does not include the following files that remain unused
even after upcoming ozone integration.

 platform/x11/x11_event_source_glib.cc
 keycodes/keyboard_code_conversion_mac.h
 keycodes/keyboard_code_conversion_mac.mm
 keycodes/keyboard_code_conversion_win.cc
 keycodes/keyboard_code_conversion_win.h
 cocoa/cocoa_event_utils.h
 cocoa/cocoa_event_utils.mm
 cocoa/events_mac.mm
 win/events_win.cc
 linux/text_edit_command_auralinux.cc
 linux/text_edit_command_auralinux.h
 linux/text_edit_key_bindings_delegate_auralinux.cc
 linux/text_edit_key_bindings_delegate_auralinux.h
 test/cocoa_test_event_utils.h
 test/cocoa_test_event_utils.mm
 gestures/blink/web_gesture_curve_impl_unittest.cc
 android/scroller*
 ozone/evdev/libgestures_glue*
 ozone/layout/xkb/
 ozone/chromeos/*
 ui/gfx/screen_ios.mm

BUG=
R=jamesr@chromium.org

Review URL: https://codereview.chromium.org/1287103004 .
diff --git a/ui/events/event_switches.h b/ui/events/event_switches.h
index ff73d9c..94bf37f 100644
--- a/ui/events/event_switches.h
+++ b/ui/events/event_switches.h
@@ -21,7 +21,8 @@
 EVENTS_BASE_EXPORT extern const char kTouchDevices[];
 #endif
 
-#if defined(USE_XI2_MT) || defined(USE_OZONE)
+#if defined(USE_X11) || defined(USE_OZONE)
+EVENTS_BASE_EXPORT extern const char kExtraTouchNoiseFiltering[];
 EVENTS_BASE_EXPORT extern const char kTouchCalibration[];
 #endif