Set compositor and CALayer background color from frames

content/browser/renderer_host/render_widget_host_view_mac.mm

 // Copyright (c) 2012 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.
 
 #include "content/browser/renderer_host/render_widget_host_view_mac.h"
 
 #import <Carbon/Carbon.h>
 #import <objc/runtime.h>
 #include <OpenGL/gl.h>
 #include <QuartzCore/QuartzCore.h>
@@ skipping 1413 matching lines @@
     NSRect bounds = NSRectFromCGRect(node_bounds_in_screen.ToCGRect());
     UAZoomChangeFocus(&bounds, NULL, kUAZoomFocusTypeOther);
   }
 }
 
 void RenderWidgetHostViewMac::OnSwapCompositorFrame(
     uint32_t compositor_frame_sink_id,
     cc::CompositorFrame frame) {
   TRACE_EVENT0("browser", "RenderWidgetHostViewMac::OnSwapCompositorFrame");
 
+  // Override the compositor background color. See RenderWidgetHostViewAura
+  // for more details.
+  SetBackgroundColor(frame.metadata.root_background_color);
+
   last_scroll_offset_ = frame.metadata.root_scroll_offset;
 
   page_at_minimum_scale_ =
       frame.metadata.page_scale_factor == frame.metadata.min_page_scale_factor;
   browser_compositor_->SwapCompositorFrame(compositor_frame_sink_id,
                                            std::move(frame));
   UpdateDisplayVSyncParameters();
 }
 
 void RenderWidgetHostViewMac::ClearCompositorFrame() {
@@ skipping 2037 matching lines @@
 
 // "-webkit-app-region: drag | no-drag" is implemented on Mac by excluding
 // regions that are not draggable. (See ControlRegionView in
 // native_app_window_cocoa.mm). This requires the render host view to be
 // draggable by default.
 - (BOOL)mouseDownCanMoveWindow {
   return YES;
 }
 
 @end