Introduce bottom controls to CC and let it respond to scrolling

content/renderer/gpu/render_widget_compositor.cc

Index: content/renderer/gpu/render_widget_compositor.cc
diff --git a/content/renderer/gpu/render_widget_compositor.cc b/content/renderer/gpu/render_widget_compositor.cc
index 900c5aa53bfb5c3a7041a26910ab685ef2cac7a4..325fe3abec7e85b2932852b41134740bd7a67049 100644
--- a/content/renderer/gpu/render_widget_compositor.cc
+++ b/content/renderer/gpu/render_widget_compositor.cc
@@ -1010,6 +1010,10 @@ void RenderWidgetCompositor::setTopControlsShownRatio(float ratio) {
   layer_tree_host_->GetLayerTree()->SetTopControlsShownRatio(ratio);
 }
 
+void RenderWidgetCompositor::setBottomControlsHeight(float height) {
+  layer_tree_host_->GetLayerTree()->SetBottomControlsHeight(height);
+}
+
 void RenderWidgetCompositor::WillBeginMainFrame() {
   delegate_->WillBeginCompositorFrame();
 }