[exp] cc: Introduce cc::CompositorMutator.

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 688 matching lines @@
         break;
       case SchedulerStateMachine::ACTION_ANIMATE: {
         // TODO(robliao): Remove ScopedTracker below once crbug.com/461509 is
         // fixed.
         tracked_objects::ScopedTracker tracking_profile2(
             FROM_HERE_WITH_EXPLICIT_FUNCTION(
                 "461509 Scheduler::ProcessScheduledActions2"));
         client_->ScheduledActionAnimate();
         break;
       }
+      case SchedulerStateMachine::ACTION_CUSTOM_MUTATE: {
+        client_->ScheduledActionCustomMutate();
+        break;
+      }
       case SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME: {
         // TODO(robliao): Remove ScopedTracker below once crbug.com/461509 is
         // fixed.
         tracked_objects::ScopedTracker tracking_profile3(
             FROM_HERE_WITH_EXPLICIT_FUNCTION(
                 "461509 Scheduler::ProcessScheduledActions3"));
         client_->ScheduledActionSendBeginMainFrame();
         break;
       }
       case SchedulerStateMachine::ACTION_COMMIT: {
@@ skipping 149 matching lines @@
 }
 
 bool Scheduler::IsBeginMainFrameSentOrStarted() const {
   return (state_machine_.commit_state() ==
               SchedulerStateMachine::COMMIT_STATE_BEGIN_MAIN_FRAME_SENT ||
           state_machine_.commit_state() ==
               SchedulerStateMachine::COMMIT_STATE_BEGIN_MAIN_FRAME_STARTED);
 }
 
 }  // namespace cc