Fixed pass-by-value to pass-by-reference

chrome/browser/tab_contents/thumbnail_generator.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_TAB_CONTENTS_THUMBNAIL_GENERATOR_H_
 #define CHROME_BROWSER_TAB_CONTENTS_THUMBNAIL_GENERATOR_H_
 #pragma once
 
 #include <map>
 #include <utility>
@@ skipping 91 matching lines @@
       ClipResult* clip_result) const;
 
   // Start or stop monitoring notifications for |renderer| based on the value
   // of |monitor|.
   void MonitorRenderer(content::RenderWidgetHost* renderer, bool monitor);
 
   // Calculates how "boring" a thumbnail is. The boring score is the
   // 0,1 ranged percentage of pixels that are the most common
   // luma. Higher boring scores indicate that a higher percentage of a
   // bitmap are all the same brightness.
-  static double CalculateBoringScore(SkBitmap* bitmap);
+  static double CalculateBoringScore(const SkBitmap& bitmap);
 
   // Gets the clipped bitmap from |bitmap| per the aspect ratio of the
   // desired width and the desired height. For instance, if the input
   // bitmap is vertically long (ex. 400x900) and the desired size is
   // square (ex. 100x100), the clipped bitmap will be the top half of the
   // input bitmap (400x400).
   static SkBitmap GetClippedBitmap(const SkBitmap& bitmap,
                                    int desired_width,
                                    int desired_height,
                                    ClipResult* clip_result);
 
   // Update the thumbnail of the given tab contents if necessary.
   void UpdateThumbnailIfNecessary(content::WebContents* webb_contents);
 
   // Update the thumbnail of the given tab.
-  void UpdateThumbnail(content::WebContents* web_contents, SkBitmap bitmap,
-      const ThumbnailGenerator::ClipResult& clip_result);
+  void UpdateThumbnail(content::WebContents* web_contents,
+                       const SkBitmap& bitmap,
+                       const ThumbnailGenerator::ClipResult& clip_result);
 
   // Returns true if we should update the thumbnail of the given URL.
   static bool ShouldUpdateThumbnail(Profile* profile,
                                     history::TopSites* top_sites,
                                     const GURL& url);
 
   // content::WebContentsObserver overrides.
   virtual void DidStartLoading() OVERRIDE;
   virtual void StopNavigation() OVERRIDE;
 
@@ skipping 22 matching lines @@
   typedef std::map<int,
                    linked_ptr<AsyncRequestInfo> > ThumbnailCallbackMap;
   ThumbnailCallbackMap callback_map_;
 
   bool load_interrupted_;
 
   DISALLOW_COPY_AND_ASSIGN(ThumbnailGenerator);
 };
 
 #endif  // CHROME_BROWSER_TAB_CONTENTS_THUMBNAIL_GENERATOR_H_