cc: Allow the main thread to cancel commits

Add a new SetNeedsUpdateLayers that triggers the commit flow, but is
abortable if update layers doesn't actually make any changes.  This
allows the main thread to abort a begin frame.  This happens in the case
of scroll updates from the compositor thread or invalidations.

There was previously an abort begin frame call for when a visibility
message and a begin frame message were posted simultaneously, but it
incorrectly applied the scrolls and scales without informing the
compositor thread that these had already been consumed.  To fix this,
the abort message passes back a boolean about whether or not the
commit was aborted (and needed to be sent again) or was handled
(and the scrolls and scales processed).

To avoid a deluge of begin frames (in the commit sense) from the
scheduler, the scheduler has been adjusted to wait until the next begin
frame (in the vsync signal sense) so that these calls can be throttled.
Otherwise, the scheduler will just keep trying to begin frame.

R=brianderson@chromium.org, danakj@chromium.org
BUG=256381

Review URL: https://chromiumcodereview.appspot.com/19106007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@213338 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 5 insertions, 1 deletions

diff --git a/cc/trees/thread_proxy.h b/cc/trees/thread_proxy.h
index eb2ef7e..c9d5b47 100644
--- a/cc/trees/thread_proxy.h
+++ b/cc/trees/thread_proxy.h
@@ -49,6 +49,7 @@ class ThreadProxy : public Proxy,
   virtual void CreateAndInitializeOutputSurface() OVERRIDE;
   virtual const RendererCapabilities& GetRendererCapabilities() const OVERRIDE;
   virtual void SetNeedsAnimate() OVERRIDE;
+  virtual void SetNeedsUpdateLayers() OVERRIDE;
   virtual void SetNeedsCommit() OVERRIDE;
   virtual void SetNeedsRedraw(gfx::Rect damage_rect) OVERRIDE;
   virtual void SetDeferCommits(bool defer_commits) OVERRIDE;
@@ -135,6 +136,7 @@ class ThreadProxy : public Proxy,
   void OnOutputSurfaceInitializeAttempted(
       bool success,
       const RendererCapabilities& capabilities);
+  void SendCommitRequestToImplThreadIfNeeded();
 
   // Called on impl thread.
   struct ReadbackRequest;
@@ -146,7 +148,7 @@ class ThreadProxy : public Proxy,
       CompletionEvent* completion,
       ResourceUpdateQueue* queue,
       scoped_refptr<cc::ContextProvider> offscreen_context_provider);
-  void BeginFrameAbortedByMainThreadOnImplThread();
+  void BeginFrameAbortedByMainThreadOnImplThread(bool did_handle);
   void RequestReadbackOnImplThread(ReadbackRequest* request);
   void FinishAllRenderingOnImplThread(CompletionEvent* completion);
   void InitializeImplOnImplThread(CompletionEvent* completion);
@@ -241,6 +243,8 @@ class ThreadProxy : public Proxy,
 
   bool inside_draw_;
 
+  bool can_cancel_commit_;
+
   bool defer_commits_;
   scoped_ptr<BeginFrameAndCommitState> pending_deferred_commit_;