[compositor-worker] Create property tree nodes for proxies.

cc/animation/mutable_properties.h

 // Copyright 2015 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_MUTABLE_PROPERTIES_H_
 #define CC_ANIMATION_MUTABLE_PROPERTIES_H_
 
 #include <stdint.h>
 
 namespace cc {
 
 struct MutableProperty {
   enum : uint32_t { kNone = 0 };
   enum : uint32_t { kOpacity = 1 << 0 };
   enum : uint32_t { kScrollLeft = 1 << 1 };
   enum : uint32_t { kScrollTop = 1 << 2 };
   enum : uint32_t { kTransform = 1 << 3 };
+  enum : uint32_t { kTransformRelated = kTransform | kScrollLeft | kScrollTop };
 
   enum : int { kNumProperties = 4 };
 };
 
 }  // namespace cc
 
 #endif  // CC_ANIMATION_MUTABLE_PROPERTIES_H_