compositor-worker: cc->blink mutation plumbing

cc/animation/layer_tree_mutations_callback.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_MUTATIONS_CALLBACK_H_
+#define CC_ANIMATION_LAYER_TREE_MUTATIONS_CALLBACK_H_
+
+namespace cc {
+
+// Represents a callback which is responsible for applying layer tree mutations.
+// The concrete implementation lives in Blink which applies mutation to DOM
+// elements.
+class LayerTreeMutationsCallback {

[enne (OOO), 2016/03/02 19:55:54]

What does this indirection get you over just using closures directly?

[majidvp, 2016/03/02 21:15:10]

The actual implementation of the method that returns the
callback lives in Source/platform. It was not clear to me if I can use
base::bind 
there yet. So I chose to return this interface and bind it in cc which seems 
to be the pattern that is being used in such situations e.g.,
|WebLayerScrollClient.h|

+ public:
+  virtual ~LayerTreeMutationsCallback() {}
+  virtual void ApplyLayerTreeMutations() = 0;
+};
+
+}  // namespace cc
+
+#endif  // CC_ANIMATION_LAYER_TREE_MUTATIONS_CALLBACK_H_