[cc] Pass on BeginFrameAcks from CompositorEBFS through RWHVAura, DFH.

cc/ipc/compositor_frame_metadata.mojom

 // Copyright 2016 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.
 
 module cc.mojom;
 
+import "cc/ipc/begin_frame_args.mojom";
 import "cc/ipc/selection.mojom";
 import "cc/ipc/surface_id.mojom";
 import "ui/events/mojo/latency_info.mojom";
 import "ui/gfx/geometry/mojo/geometry.mojom";
 
 // See cc/output/compositor_frame_metadata.h.
 struct CompositorFrameMetadata {
   float device_scale_factor;
   gfx.mojom.Vector2dF root_scroll_offset;
   float page_scale_factor;
   gfx.mojom.SizeF scrollable_viewport_size;
   gfx.mojom.SizeF root_layer_size;
   float min_page_scale_factor;
   float max_page_scale_factor;
   bool root_overflow_x_hidden;
   bool root_overflow_y_hidden;
   bool may_contain_video;
   bool is_resourceless_software_draw_with_scroll_or_animation;
   float top_controls_height;
   float top_controls_shown_ratio;
   float bottom_controls_height;
   float bottom_controls_shown_ratio;
   uint32 root_background_color;
   Selection selection;
   array<ui.mojom.LatencyInfo> latency_info;
   array<SurfaceId> referenced_surfaces;
   bool can_activate_before_dependencies;
   uint32 content_source_id;
+  BeginFrameAck begin_frame_ack;
 };