tree 8a6dde69bec1e54f8d01b610f63f99f6bf960a95
parent 8d66e0d091ffaf332a1ea75d6c37232ad9f3ec36
author Jeff Brown <jeffbrown@google.com> 1463775462 -0700
committer Jeff Brown <jeffbrown@google.com> 1463775462 -0700

Mozart: Improve tracing and backpressure.

Refactored the GPU Output to clarify the separation of concerns
between the output and rasterizer classes.  GpuOutput maintains
the queue of frames to draw and keeps track of how many frames
are outstanding.  GpuRasterizer manages the GL context and issues
the actual drawing commands.

Simplified the policy for dropping frames so it only happen in
one spot in the compositor.  The compositor maintains a queue
of drawn frames awaiting finish.  When that queue's size exceeds
the maximum allowable pipeline depth (configurable using
the --pipeline-depth argument) a pending frame will be discarded.

Added more trace events to help understand the behavior of the
compositor.

Normalized the nomenclature for different stages in composition.
They are now called...

  - Present: accept and validate scene updates published by apps
  - Snapshot: resolve scene dependencies and capture the state
              of the scene graph for traversal
  - Paint: record drawing commands for a frame (as an SkPicture)
  - Submit: enqueue a frame to be rasterized
  - Draw: rasterize the frame

There's still much to be improved here.

BUG=
R=mikejurka@google.com

Review URL: https://codereview.chromium.org/1995873002 .