Use black for resize gutter in tab fullscreen mode.

content/browser/renderer_host/render_widget_host_view_mac.h

 // 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.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_
 
 #import <Cocoa/Cocoa.h>
 #include <IOSurface/IOSurface.h>
 #include <stddef.h>
@@ skipping 475 matching lines @@
   void UpdateBackingStoreProperties();
 
   // Ensure that the display link is associated with the correct display.
   void UpdateDisplayLink();
 
   void PauseForPendingResizeOrRepaintsAndDraw();
 
   // DelegatedFrameHostClient implementation.
   ui::Layer* DelegatedFrameHostGetLayer() const override;
   bool DelegatedFrameHostIsVisible() const override;
+  SkColor DelegatedFrameHostGetGutterColor(SkColor color) const override;
   gfx::Size DelegatedFrameHostDesiredSizeInDIP() const override;
   bool DelegatedFrameCanCreateResizeLock() const override;
   std::unique_ptr<ResizeLock> DelegatedFrameHostCreateResizeLock(
       bool defer_compositor_lock) override;
   void DelegatedFrameHostResizeLockWasReleased() override;
   void DelegatedFrameHostSendCompositorSwapAck(
       int output_surface_id,
       const cc::CompositorFrameAck& ack) override;
   void DelegatedFrameHostSendReclaimCompositorResources(
       int output_surface_id,
@@ skipping 112 matching lines @@
 
   // Factory used to safely scope delayed calls to ShutdownHost().
   base::WeakPtrFactory<RenderWidgetHostViewMac> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewMac);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_