Use black for resize gutter in tab fullscreen mode.

content/browser/renderer_host/delegated_frame_host.h

Index: content/browser/renderer_host/delegated_frame_host.h
diff --git a/content/browser/renderer_host/delegated_frame_host.h b/content/browser/renderer_host/delegated_frame_host.h
index 9f2b1813accfc8aa4926a0ce6e81317bc0f5eec3..e52d9db961115a7e5211c8ee54aafbae2ed98963 100644
--- a/content/browser/renderer_host/delegated_frame_host.h
+++ b/content/browser/renderer_host/delegated_frame_host.h
@@ -55,6 +55,10 @@ class CONTENT_EXPORT DelegatedFrameHostClient {
  public:
   virtual ui::Layer* DelegatedFrameHostGetLayer() const = 0;
   virtual bool DelegatedFrameHostIsVisible() const = 0;
+
+  // Returns the color that the resize gutters should be drawn with. Takes the
+  // suggested color from the current page background.
+  virtual SkColor DelegatedFrameHostGetGutterColor(SkColor color) const = 0;
   virtual gfx::Size DelegatedFrameHostDesiredSizeInDIP() const = 0;
 
   virtual bool DelegatedFrameCanCreateResizeLock() const = 0;
@@ -202,6 +206,8 @@ class CONTENT_EXPORT DelegatedFrameHost
   // Checks if the resize lock can be released because we received an new frame.
   void CheckResizeLock();
 
+  SkColor GetGutterColor() const;
+
   // Update the layers for the resize gutters to the right and bottom of the
   // surface layer.
   void UpdateGutters();