Introduce bottom controls to CC and let it respond to scrolling

cc/ipc/compositor_frame_metadata.mojom

Index: cc/ipc/compositor_frame_metadata.mojom
diff --git a/cc/ipc/compositor_frame_metadata.mojom b/cc/ipc/compositor_frame_metadata.mojom
index 8db3460dd018d915ac00f0e03cbf51f2f24952dc..8d294e3d0eac68ef1627f7339a997112130f6594 100644
--- a/cc/ipc/compositor_frame_metadata.mojom
+++ b/cc/ipc/compositor_frame_metadata.mojom
@@ -20,8 +20,10 @@ struct CompositorFrameMetadata {
   float max_page_scale_factor;
   bool root_overflow_x_hidden;
   bool root_overflow_y_hidden;
-  gfx.mojom.Vector2dF location_bar_offset;
-  gfx.mojom.Vector2dF location_bar_content_translation;
+  gfx.mojom.Vector2dF top_controls_height;
+  float top_controls_shown_ratio;
+  gfx.mojom.Vector2dF bottom_controls_height;
+  float bottom_controls_shown_ratio;
   uint32 root_background_color;
   Selection selection;
   array<ui.mojom.LatencyInfo> latency_info;