Create a new action triggered when a BeginMainFrame is not expected before vsync

cc/scheduler/scheduler.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 <algorithm>
 
 #include "base/auto_reset.h"
 #include "base/logging.h"
@@ skipping 611 matching lines @@
       case SchedulerStateMachine::ACTION_NONE:
         break;
       case SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME:
         compositor_timing_history_->WillBeginMainFrame(
             begin_main_frame_args_.on_critical_path,
             begin_main_frame_args_.frame_time);
         state_machine_.WillSendBeginMainFrame();
         // TODO(brianderson): Pass begin_main_frame_args_ directly to client.
         client_->ScheduledActionSendBeginMainFrame(begin_main_frame_args_);
         break;
+      case SchedulerStateMachine::ACTION_DO_IDLE_WORK:
+        state_machine_.WillDoIdleWork();
+        BeginImplFrameNotExpectedSoon();

[Sami, 2017/03/20 16:58:49]

Let's introduce a new notification which kicks off a short idle period rather
than a long one to avoid accidental jank.

+        break;
       case SchedulerStateMachine::ACTION_COMMIT: {
         bool commit_has_no_updates = false;
         state_machine_.WillCommit(commit_has_no_updates);
         client_->ScheduledActionCommit();
         break;
       }
       case SchedulerStateMachine::ACTION_ACTIVATE_SYNC_TREE:
         compositor_timing_history_->WillActivate();
         state_machine_.WillActivate();
         client_->ScheduledActionActivateSyncTree();
@@ skipping 157 matching lines @@
 }
 
 BeginFrameAck Scheduler::CurrentBeginFrameAckForActiveTree() const {
   return BeginFrameAck(
       begin_main_frame_args_.source_id, begin_main_frame_args_.sequence_number,
       state_machine_.last_begin_frame_sequence_number_active_tree_was_fresh(),
       0, true);
 }
 
 }  // namespace cc