Introduce bottom controls to CC and let it respond to scrolling

cc/ipc/compositor_frame_metadata_struct_traits.h

Index: cc/ipc/compositor_frame_metadata_struct_traits.h
diff --git a/cc/ipc/compositor_frame_metadata_struct_traits.h b/cc/ipc/compositor_frame_metadata_struct_traits.h
index c7e4f46897392e48b8affdec28c4d77be2a01fe1..00feb6896cc9fb9d783c2eaf6d1fc2481a75571e 100644
--- a/cc/ipc/compositor_frame_metadata_struct_traits.h
+++ b/cc/ipc/compositor_frame_metadata_struct_traits.h
@@ -57,14 +57,24 @@ struct StructTraits<cc::mojom::CompositorFrameMetadata,
     return metadata.root_overflow_y_hidden;
   }
 
-  static gfx::Vector2dF location_bar_offset(
+  static gfx::Vector2dF top_bar_translate(
       const cc::CompositorFrameMetadata& metadata) {
-    return metadata.location_bar_offset;
+    return metadata.top_bar_translate;
   }
 
-  static gfx::Vector2dF location_bar_content_translation(
+  static gfx::Vector2dF top_bar_shown(
       const cc::CompositorFrameMetadata& metadata) {
-    return metadata.location_bar_content_translation;
+    return metadata.top_bar_shown;
+  }
+
+  static gfx::Vector2dF bottom_bar_translate(
+      const cc::CompositorFrameMetadata& metadata) {
+    return metadata.bottom_bar_translate;
+  }
+
+  static gfx::Vector2dF bottom_bar_shown(
+      const cc::CompositorFrameMetadata& metadata) {
+    return metadata.bottom_bar_shown;
   }
 
   static uint32_t root_background_color(
@@ -108,9 +118,8 @@ struct StructTraits<cc::mojom::CompositorFrameMetadata,
     out->max_page_scale_factor = data.max_page_scale_factor();
     out->root_overflow_x_hidden = data.root_overflow_x_hidden();
     out->root_overflow_y_hidden = data.root_overflow_y_hidden();
-    if (!data.ReadLocationBarOffset(&out->location_bar_offset) ||
-        !data.ReadLocationBarContentTranslation(
-            &out->location_bar_content_translation)) {
+    if (!data.ReadTopBarTranslate(&out->top_bar_translate) ||
+        !data.ReadTopBarShown(&out->top_bar_shown)) {
       return false;
     }