Pass the overdraw value to the browser w/ frame

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),
-      page_scale_factor(0),
-      min_page_scale_factor(0),
-      max_page_scale_factor(0) {
+    : 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) {
 }
 
 CompositorFrameMetadata::~CompositorFrameMetadata() {
 }
 
 }  // namespace cc