Introduce bottom controls to CC and let it respond to scrolling

cc/trees/layer_tree_host.cc

 // Copyright 2011 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/trees/layer_tree_host.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 498 matching lines @@
       page_scale_factor_, min_page_scale_factor_, max_page_scale_factor_);
   sync_tree->elastic_overscroll()->PushFromMainThread(elastic_overscroll_);
   if (sync_tree->IsActiveTree())
     sync_tree->elastic_overscroll()->PushPendingToActive();
 
   sync_tree->PassSwapPromises(std::move(swap_promise_list_));
 
   sync_tree->set_top_controls_shrink_blink_size(
       top_controls_shrink_blink_size_);
   sync_tree->set_top_controls_height(top_controls_height_);
+  sync_tree->set_bottom_controls_height(bottom_controls_height_);

[Khushal, 2016/08/17 04:45:34]

The commit step now happens in LayerTree::PushPropertiesTo.

   sync_tree->PushTopControlsFromMainThread(top_controls_shown_ratio_);
 
   host_impl->SetHasGpuRasterizationTrigger(has_gpu_rasterization_trigger_);
   host_impl->SetContentIsSuitableForGpuRasterization(
       content_is_suitable_for_gpu_rasterization_);
   RecordGpuRasterizationHistogram();
 
   host_impl->SetViewportSize(device_viewport_size_);
   // TODO(senorblanco): Move this up so that it happens before GPU rasterization
   // properties are set, since those trigger an update of GPU rasterization
@@ skipping 291 matching lines @@
 }
 
 void LayerTreeHost::SetTopControlsShownRatio(float ratio) {
   if (top_controls_shown_ratio_ == ratio)
     return;
 
   top_controls_shown_ratio_ = ratio;
   SetNeedsCommit();
 }
 
+void LayerTreeHost::setBottomControlHeight(float height) {
+  if (bottom_controls_height_ == height)
+    return;
+
+  bottom_controls_height_ = height;
+  SetNeedsCommit();
+}
+
 void LayerTreeHost::ApplyPageScaleDeltaFromImplSide(float page_scale_delta) {
   DCHECK(CommitRequested());
   if (page_scale_delta == 1.f)
     return;
   page_scale_factor_ *= page_scale_delta;
   SetPropertyTreesNeedRebuild();
 }
 
 void LayerTreeHost::SetPageScaleFactorAndLimits(float page_scale_factor,
                                                 float min_page_scale_factor,
@@ skipping 831 matching lines @@
 
   surface_client_id_ = proto.surface_client_id();
   next_surface_sequence_ = proto.next_surface_sequence();
 }
 
 AnimationHost* LayerTreeHost::animation_host() const {
   return layer_tree_.animation_host();
 }
 
 }  // namespace cc