cc: Allow the main thread to cancel commits

cc/scheduler/scheduler_unittest.cc

 // Copyright 2011 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 "cc/scheduler/scheduler.h"
 
 #include <string>
 #include <vector>
 
 #include "base/logging.h"
@@ skipping 360 matching lines @@
   scheduler->SetMainThreadNeedsLayerTextures();
   scheduler->SetNeedsCommit();
   client.Reset();
   // Verify that pending texture acquisition fires when visibility
   // is lost in order to avoid a deadlock.
   scheduler->SetVisible(false);
   EXPECT_SINGLE_ACTION("ScheduledActionAcquireLayerTexturesForMainThread",
                        client);
   client.Reset();
 
+  // Already sent a begin frame on this current frame, so wait.
+  scheduler->SetVisible(true);
+  EXPECT_EQ(0, client.num_actions_());
+  client.Reset();
+
   // Regaining visibility with textures acquired by main thread while
   // compositor is waiting for first draw should result in a request
   // for a new frame in order to escape a deadlock.
-  scheduler->SetVisible(true);
-  EXPECT_SINGLE_ACTION("ScheduledActionSendBeginFrameToMainThread", client);
+  scheduler->BeginFrame(BeginFrameArgs::CreateForTesting());

[danakj, 2013/07/17 20:53:24]

I'm having trouble convincing myself that we will cause this BeginFrame to
happen here. Why wasn't there a SetNeedsBeginFrameOnImplThread before this after
SetVisible(true)?

[enne (OOO), 2013/07/18 17:36:37]

Different begin frames.  SetNeedsBeginFrameOnImplThread is set in response to
scheduler->BeginFrame above.  Because that didn't happen in the old code, there
was no need for it.

+  EXPECT_ACTION("ScheduledActionSendBeginFrameToMainThread", client, 0, 2);
+  EXPECT_ACTION("SetNeedsBeginFrameOnImplThread", client, 1, 2);
   client.Reset();
 }
 
 class SchedulerClientThatsetNeedsDrawInsideDraw : public FakeSchedulerClient {
  public:
   virtual void ScheduledActionSendBeginFrameToMainThread() OVERRIDE {}
   virtual ScheduledActionDrawAndSwapResult
   ScheduledActionDrawAndSwapIfPossible() OVERRIDE {
     // Only SetNeedsRedraw the first time this is called
     if (!num_draws_)
@@ skipping 217 matching lines @@
 
   // Get the compositor to do a ScheduledActionDrawAndSwapForced.
   scheduler->SetCanDraw(true);
   scheduler->SetNeedsRedraw();
   scheduler->SetNeedsForcedRedraw();
   EXPECT_TRUE(client.HasAction("ScheduledActionDrawAndSwapForced"));
 }
 
 }  // namespace
 }  // namespace cc