Make cc::CompositorFrames movable [Part 1 of 2]

cc/output/compositor_frame.cc

 // Copyright 2012 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/output/compositor_frame.h"
 
 namespace cc {
 
 CompositorFrame::CompositorFrame() {}
 
+CompositorFrame::CompositorFrame(CompositorFrame&& other) = default;
+
 CompositorFrame::~CompositorFrame() {}
 
-void CompositorFrame::AssignTo(CompositorFrame* target) {
-  target->delegated_frame_data = std::move(delegated_frame_data);
-  target->gl_frame_data = std::move(gl_frame_data);
-  target->metadata = metadata;
-}
+CompositorFrame& CompositorFrame::operator=(CompositorFrame&& other) = default;
 
 }  // namespace cc