cc: Implement deadline scheduling disabled by default

cc/output/begin_frame_args.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/begin_frame_args.h"
 
 namespace cc {
 
 BeginFrameArgs::BeginFrameArgs()
   : frame_time(base::TimeTicks()),
@@ skipping 30 matching lines @@
                         DefaultInterval());
 }
 
 BeginFrameArgs BeginFrameArgs::CreateExpiredForTesting() {
   base::TimeTicks now = base::TimeTicks::Now();
   return BeginFrameArgs(now,
                         now - DefaultInterval(),
                         DefaultInterval());
 }
 
+// This is a hard-coded deadline adjustment that assumes 60Hz, to be used in
+// cases where a good estimated draw time is not known. Using 1/3 of the vsync
+// as the default adjustment gives the Browser the last 1/3 of a frame to
+// produce output, the Renderer Impl thread the middle 1/3 of a frame to produce
+// ouput, and the Renderer Main thread the first 1/3 of a frame to produce
+// output.
 base::TimeDelta BeginFrameArgs::DefaultDeadlineAdjustment() {
-  // Using a large deadline adjustment will effectively revert BeginFrame
-  // scheduling to the hard vsync scheduling we used to have.
-  return base::TimeDelta::FromSeconds(-1);
+  return base::TimeDelta::FromMicroseconds(-16666 / 3);
 }
 
 base::TimeDelta BeginFrameArgs::DefaultInterval() {
   return base::TimeDelta::FromMicroseconds(16666);
 }
 
 base::TimeDelta BeginFrameArgs::DefaultRetroactiveBeginFramePeriod() {
   return base::TimeDelta::FromMicroseconds(4444);
 }
 
-
 }  // namespace cc