cc: Always use SetNeedsBeginFrame to request the next BeginFrame

cc/output/output_surface_unittest.cc

 // Copyright 2013 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/output/output_surface.h"
 
 #include "base/test/test_simple_task_runner.h"
 #include "cc/debug/test_context_provider.h"
 #include "cc/debug/test_web_graphics_context_3d.h"
 #include "cc/output/managed_memory_policy.h"
@@ skipping 192 matching lines @@
   // BeginFrame should be called on the first tick.
   task_runner->RunPendingTasks();
   EXPECT_EQ(client.begin_frame_count(), 1);
   EXPECT_EQ(output_surface.pending_swap_buffers(), 0);
 
   // BeginFrame should not be called when there is a pending BeginFrame.
   task_runner->RunPendingTasks();
   EXPECT_EQ(client.begin_frame_count(), 1);
   EXPECT_EQ(output_surface.pending_swap_buffers(), 0);
 
   // DidSwapBuffers should clear the pending BeginFrame.

[danakj, 2013/09/12 16:53:59]

comment should be replaced?

[brianderson, 2013/09/12 18:46:44]

Yes. I will comb the code for similar comments to remove.

   output_surface.DidSwapBuffersForTesting();
+  output_surface.SetNeedsBeginFrame(true);
   EXPECT_EQ(client.begin_frame_count(), 1);
   EXPECT_EQ(output_surface.pending_swap_buffers(), 1);
   task_runner->RunPendingTasks();
   EXPECT_EQ(client.begin_frame_count(), 2);
   EXPECT_EQ(output_surface.pending_swap_buffers(), 1);
 
   // BeginFrame should be throttled by pending swap buffers.

[danakj, 2013/09/12 16:53:59]

So if it's not tied to swap, what will throttle begin frame if swap is not
called?

[brianderson, 2013/09/12 18:46:44]

The OutputSurface will throttle sending the next BeginFrame until
SetNeedsBeginFrame(true) has been called. There are already instances where we
do not swap and the Scheduler requests another BeginFrame by calling
SetNeedsBeginFrame(true). This patch just makes it so that it is the one and
only way to get another BeginFrame.

   output_surface.DidSwapBuffersForTesting();
+  output_surface.SetNeedsBeginFrame(true);
   EXPECT_EQ(client.begin_frame_count(), 2);
   EXPECT_EQ(output_surface.pending_swap_buffers(), 2);
   task_runner->RunPendingTasks();
   EXPECT_EQ(client.begin_frame_count(), 2);
   EXPECT_EQ(output_surface.pending_swap_buffers(), 2);
 
   // SwapAck should decrement pending swap buffers and unblock BeginFrame again.
   output_surface.OnSwapBuffersCompleteForTesting();
   EXPECT_EQ(client.begin_frame_count(), 2);
   EXPECT_EQ(output_surface.pending_swap_buffers(), 1);
@@ skipping 44 matching lines @@
   // BeginFrames...
   output_surface.BeginFrameForTesting();
   EXPECT_EQ(client.begin_frame_count(), 1);
   // ...and retroactively triggered by a SetNeedsBeginFrame.
   output_surface.SetNeedsBeginFrame(true);
   EXPECT_EQ(client.begin_frame_count(), 2);
   // ...or retroactively triggered by a Swap.
   output_surface.BeginFrameForTesting();
   EXPECT_EQ(client.begin_frame_count(), 2);
   output_surface.DidSwapBuffersForTesting();
+  output_surface.SetNeedsBeginFrame(true);
   EXPECT_EQ(client.begin_frame_count(), 3);
   EXPECT_EQ(output_surface.pending_swap_buffers(), 1);
 
   // Optimistically injected BeginFrames should be by throttled by pending
   // swap buffers...
   output_surface.DidSwapBuffersForTesting();
+  output_surface.SetNeedsBeginFrame(true);
   EXPECT_EQ(client.begin_frame_count(), 3);
   EXPECT_EQ(output_surface.pending_swap_buffers(), 2);
   output_surface.BeginFrameForTesting();
   EXPECT_EQ(client.begin_frame_count(), 3);
   // ...and retroactively triggered by OnSwapBuffersComplete
   output_surface.OnSwapBuffersCompleteForTesting();
   EXPECT_EQ(client.begin_frame_count(), 4);
 }
 
 TEST(OutputSurfaceTest, RetroactiveBeginFrameDoesNotDoubleTickWhenEmulating) {
@@ skipping 99 matching lines @@
 
   // 0 bytes limit should be ignored.
   policy.bytes_limit_when_visible = 0;
   context_provider->SetMemoryAllocation(policy,
                                         discard_backbuffer_when_not_visible);
   EXPECT_EQ(1234u, client.memory_policy().bytes_limit_when_visible);
 }
 
 }  // namespace
 }  // namespace cc