Replace overdraw_bottom_height with top_controls_layout_height.

cc/output/compositor_frame_metadata.cc

 // Copyright (c) 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_metadata.h"
 
 namespace cc {
 
 CompositorFrameMetadata::CompositorFrameMetadata()
     : device_scale_factor(0.f),
       page_scale_factor(0.f),
       min_page_scale_factor(0.f),
-      max_page_scale_factor(0.f),
-      overdraw_bottom_height(0.f) {
+      max_page_scale_factor(0.f) {
 }
 
 CompositorFrameMetadata::~CompositorFrameMetadata() {
 }
 
 }  // namespace cc