Introduce bottom controls to CC and let it respond to scrolling

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 053ae8028000cff6ff1c0d18d8a862866f76b094..3442339eeb55a735831c83beb768bbdb9af7f4a3 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -1586,6 +1586,10 @@ CompositorFrameMetadata LayerTreeHostImpl::MakeCompositorFrameMetadata() const {
       gfx::Vector2dF(0.f, top_controls_manager_->ControlsTopOffset());
   metadata.location_bar_content_translation =
       gfx::Vector2dF(0.f, top_controls_manager_->ContentTopOffset());
+  metadata.bottom_bar_offset =
+      gfx::Vector2dF(0.f, top_controls_manager_->BottomControlsOffset());
+  metadata.bottom_bar_content_translation =
+      gfx::Vector2dF(0.f, top_controls_manager_->BottomContentOffset());
   metadata.root_background_color = active_tree_->background_color();
 
   active_tree_->GetViewportSelection(&metadata.selection);
@@ -1893,6 +1897,12 @@ void LayerTreeHostImpl::UpdateViewportContainerSizes() {
           : 0.f;
   float delta_from_top_controls =
       top_controls_layout_height - top_controls_manager_->ContentTopOffset();
+  float bottom_controls_layout_height =
+      active_tree_->top_controls_shrink_blink_size()
+          ? active_tree_->bottom_controls_height()
+          : 0.f;
+  delta_from_top_controls += bottom_controls_layout_height -
+                             top_controls_manager_->BottomControlsOffset();
 
   // Adjust the viewport layers by shrinking/expanding the container to account
   // for changes in the size (e.g. top controls) since the last resize from
@@ -2447,6 +2457,10 @@ float LayerTreeHostImpl::TopControlsHeight() const {
   return active_tree_->top_controls_height();
 }
 
+float LayerTreeHostImpl::BottomControlsHeight() const {
+  return active_tree_->bottom_controls_height();
+}
+
 void LayerTreeHostImpl::SetCurrentTopControlsShownRatio(float ratio) {
   if (active_tree_->SetCurrentTopControlsShownRatio(ratio))
     DidChangeTopControlsPosition();