[compositorworker] compositor proxy mutation updates underlying layers

cc/animation/layer_tree_mutator.h

 // Copyright 2016 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.
 
 #ifndef CC_ANIMATION_LAYER_TREE_MUTATOR_H_
 #define CC_ANIMATION_LAYER_TREE_MUTATOR_H_
 
 #include "base/callback_forward.h"
 #include "base/time/time.h"
 #include "cc/base/cc_export.h"
 
 namespace cc {
 
 class LayerTreeImpl;
 
 class LayerTreeMutatorClient {
  public:
   // This is necessary because it forces an impl frame. We couldn't, for
   // example, just assume that we will "always mutate" and early-out in the
   // mutator if there was nothing to do because we won't always be producing
   // impl frames.
   virtual void SetNeedsMutate() = 0;
 };
 
 class CC_EXPORT LayerTreeMutator {
  public:
   virtual ~LayerTreeMutator() {}
 
   // Returns true if the mutator should be rescheduled.
-  virtual bool Mutate(base::TimeTicks now) = 0;
+  virtual bool Mutate(base::TimeTicks now, LayerTreeImpl* tree_impl) = 0;
   virtual void SetClient(LayerTreeMutatorClient* client) = 0;
 
   // Returns a callback which is responsible for applying layer tree mutations
   // to DOM elements.
   virtual base::Closure TakeMutations() = 0;
 };
 
 }  // namespace cc
 
 #endif  // CC_ANIMATION_LAYER_TREE_MUTATOR_H_