Make WebContentsDelegate::OpenColorChooser return NULL on failure

content/public/browser/web_contents_delegate.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_PUBLIC_BROWSER_WEB_CONTENTS_DELEGATE_H_
 #define CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_DELEGATE_H_
 
 #include <set>
 #include <string>
 
@@ skipping 317 matching lines @@
   // Invoked when navigating to a pending entry. When invoked the
   // NavigationController has configured its pending entry, but it has not yet
   // been committed.
   virtual void DidNavigateToPendingEntry(WebContents* source) {}
 
   // Returns a pointer to a service to manage JavaScript dialogs. May return
   // NULL in which case dialogs aren't shown.
   virtual JavaScriptDialogManager* GetJavaScriptDialogManager();
 
   // Called when color chooser should open. Returns the opened color chooser.
-  // Ownership of the returned pointer is transferred to the caller.
+  // Returns NULL if we failed to open the color chooser (e.g. when there is a
+  // ColorChooserDialog already open on Windows). Ownership of the returned
+  // pointer is transferred to the caller.
   virtual ColorChooser* OpenColorChooser(
       WebContents* web_contents,
       SkColor color,
       const std::vector<ColorSuggestion>& suggestions);
 
   // Called when a file selection is to be done.
   virtual void RunFileChooser(WebContents* web_contents,
                               const FileChooserParams& params) {}
 
   // Request to enumerate a directory.  This is equivalent to running the file
@@ skipping 125 matching lines @@
   // Called when |this| is no longer the WebContentsDelegate for |source|.
   void Detach(WebContents* source);
 
   // The WebContents that this is currently a delegate for.
   std::set<WebContents*> attached_contents_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_DELEGATE_H_