[exp] cc: Introduce cc::CompositorMutator.

cc/trees/thread_proxy.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/trees/thread_proxy.h"
 
 #include <algorithm>
 #include <string>
 
 #include "base/auto_reset.h"
@@ skipping 934 matching lines @@
   TRACE_EVENT0("cc", "ThreadProxy::ScheduledActionAnimate");
   DCHECK(IsImplThread());
 
   // Don't animate if there is no root layer.
   // TODO(mithro): Both Animate and UpdateAnimationState already have a
   // "!active_tree_->root_layer()" check?
   if (!impl().layer_tree_host_impl->active_tree()->root_layer()) {
     return;
   }
 
-  impl().animation_time =
+  base::TimeTicks animation_time =
       impl().layer_tree_host_impl->CurrentBeginFrameArgs().frame_time;
-  impl().layer_tree_host_impl->Animate(impl().animation_time);
+  impl().layer_tree_host_impl->Animate(animation_time);
 
   // If animations are not visible, update the state now as
   // ScheduledActionDrawAndSwapIfPossible will never be called.
   if (!impl().layer_tree_host_impl->AnimationsAreVisible()) {
     impl().layer_tree_host_impl->UpdateAnimationState(true);
   }
 }
 
+void ThreadProxy::ScheduledActionCustomMutate() {
+  // ...
+  base::TimeTicks frame_time =
+      impl().layer_tree_host_impl->CurrentBeginFrameArgs().frame_time;
+  impl().layer_tree_host_impl->ApplyCustomMutations(frame_time);
+  // ...
+}
+
 void ThreadProxy::ScheduledActionCommit() {
   TRACE_EVENT0("cc", "ThreadProxy::ScheduledActionCommit");
   DCHECK(IsImplThread());
   DCHECK(IsMainThreadBlocked());
   DCHECK(impl().commit_completion_event);
   DCHECK(impl().current_resource_update_controller);
 
   // Complete all remaining texture updates.
   impl().current_resource_update_controller->Finalize();
   impl().current_resource_update_controller = nullptr;
@@ skipping 387 matching lines @@
 }
 
 void ThreadProxy::DidCompletePageScaleAnimationOnImplThread() {
   DCHECK(IsImplThread());
   Proxy::MainThreadTaskRunner()->PostTask(
       FROM_HERE, base::Bind(&ThreadProxy::DidCompletePageScaleAnimation,
                             main_thread_weak_ptr_));
 }
 
 }  // namespace cc