[exp] cc: Introduce cc::CompositorMutator.

cc/trees/layer_tree_host_common.h

 // 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.
 
 #ifndef CC_TREES_LAYER_TREE_HOST_COMMON_H_
 #define CC_TREES_LAYER_TREE_HOST_COMMON_H_
 
 #include <limits>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/memory/ref_counted.h"
 #include "cc/base/cc_export.h"
 #include "cc/base/scoped_ptr_vector.h"
 #include "cc/layers/layer_lists.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/vector2d.h"
 #include "ui/gfx/transform.h"
 
 namespace cc {
 
 class LayerImpl;
 class Layer;
 class SwapPromise;
 
+enum class MutationProperty {
+  MUTATION_PROPERTY_TRANSFORM = 1,
+  MUTATION_PROPERTY_OPACITY,
+};
+
+union MutationValue {
+  struct {
+    int old_value;
+    int new_value;
+  } i;
+
+  struct {
+    float old_value;
+    float new_value;
+  } f;
+};
+
+struct Mutation {
+  Mutation();
+  ~Mutation();
+
+  int proxy_id;
+  int mutated_properties;

[loyso (OOO), 2015/03/20 02:38:14]

Could you elaborate how we refer/identify properties?
How we apply updates? Thanks in advance!

+  std::vector<MutationValue> mutated_values;
+};
+
+class CompositorMutator {
+ public:
+  virtual ~CompositorMutator() {}
+
+  virtual void ApplyCustomMutations(base::TimeTicks monotonic_time,
+                                    const std::vector<Mutation>& mutations) = 0;
+};
+
 class CC_EXPORT LayerTreeHostCommon {
  public:
   static gfx::Rect CalculateVisibleRect(const gfx::Rect& target_surface_rect,
                                         const gfx::Rect& layer_bound_rect,
                                         const gfx::Transform& transform);
 
   template <typename LayerType, typename RenderSurfaceLayerListType>
   struct CalcDrawPropsInputs {
    public:
     CalcDrawPropsInputs(LayerType* root_layer,
@@ skipping 242 matching lines @@
           true,
           render_surface_layer_list,
           0) {
   DCHECK(root_layer);
   DCHECK(render_surface_layer_list);
 }
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_COMMON_H_