Make some updates to extension iconography.

chrome/browser/ui/webui/extensions/extension_icon_source.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 CHROME_BROWSER_UI_WEBUI_EXTENSIONS_EXTENSION_ICON_SOURCE_H_
 #define CHROME_BROWSER_UI_WEBUI_EXTENSIONS_EXTENSION_ICON_SOURCE_H_
 
 #include <map>
 #include <string>
 
@@ skipping 38 matching lines @@
 //  2) If a 16px icon was requested, the favicon for extension's launch URL.
 //  3) The default extension / application icon if there are still no matches.
 //
 class ExtensionIconSource : public content::URLDataSource,
                             public base::SupportsWeakPtr<ExtensionIconSource> {
  public:
   explicit ExtensionIconSource(Profile* profile);
 
   // Gets the URL of the |extension| icon in the given |icon_size|, falling back
   // based on the |match| type. If |grayscale|, the URL will be for the
-  // desaturated version of the icon. |exists|, if non-NULL, will be set to true
-  // if the icon exists; false if it will lead to a default or not-present
-  // image.
+  // desaturated version of the icon.
   static GURL GetIconURL(const Extension* extension,
                          int icon_size,
                          ExtensionIconSet::MatchType match,
-                         bool grayscale,
-                         bool* exists);
+                         bool grayscale);
 
   // A public utility function for accessing the bitmap of the image specified
   // by |resource_id|.
   static SkBitmap* LoadImageByResourceId(int resource_id);
 
   // content::URLDataSource implementation.
   std::string GetSource() const override;
   std::string GetMimeType(const std::string&) const override;
   void StartDataRequest(
       const std::string& path,
@@ skipping 79 matching lines @@
   std::unique_ptr<SkBitmap> default_extension_data_;
 
   base::CancelableTaskTracker cancelable_task_tracker_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionIconSource);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_UI_WEBUI_EXTENSIONS_EXTENSION_ICON_SOURCE_H_