Refactored-out the code of thumbnaling algorithm from thumbnail_tab_helper.

chrome/browser/thumbnails/thumbnail_service.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_THUMBNAILS_THUMBNAIL_SERVICE_H_
 #define CHROME_BROWSER_THUMBNAILS_THUMBNAIL_SERVICE_H_
 
 #include "chrome/browser/profiles/refcounted_profile_keyed_service.h"
 #include "chrome/common/thumbnail_score.h"
 #include "googleurl/src/gurl.h"
 #include "ui/gfx/image/image.h"
 
 namespace base {
 class RefCountedMemory;
 }
 
 namespace thumbnails {
 
+class ThumbnailingAlgorithm;
+struct ThumbnailingContext;
+
 // An interface abstracting access to thumbnails. Intended as a temporary
 // bridge facilitating switch from TopSites as the thumbnail source to a more
 // robust way of handling these artefacts.
 class ThumbnailService : public RefcountedProfileKeyedService {
  public:
   // Sets the given thumbnail for the given URL. Returns true if the thumbnail
   // was updated. False means either the URL wasn't known to us, or we felt
   // that our current thumbnail was superior to the given one.
-  virtual bool SetPageThumbnail(const GURL& url,
-                                const gfx::Image& thumbnail,
-                                const ThumbnailScore& score) = 0;
+  virtual bool SetPageThumbnail(const ThumbnailingContext& context,
+                                const gfx::Image& thumbnail) = 0;
+
+  // Create and return a new instance of the algorithm. They encapsulate the

[sky, 2013/01/22 16:10:28]

This is still implying ThumbnailingAlgorithm is something the caller should own
and need not be ref counted. I think you want:

// Returns the ThumbnailingAlgorithm used for processing thumbnails.

And name it GetThumbnailingAlgorithm().

[motek., 2013/01/22 16:56:19]

Done.

+  // process of creating a thumbnail from tab contents. The lifetime of these
+  // instances is limited to the act of processing a single tab image. They
+  // are permitted to hold the state of such process.
+  virtual ThumbnailingAlgorithm* CreateThumbnailingAlgorithm() const = 0;
 
   // Gets a thumbnail for a given page. Returns true iff we have the thumbnail.
   // This may be invoked on any thread.
   // As this method may be invoked on any thread the ref count needs to be
   // incremented before this method returns, so this takes a scoped_refptr*.
   virtual bool GetPageThumbnail(
       const GURL& url,
       scoped_refptr<base::RefCountedMemory>* bytes) = 0;
 
   // Returns true if the page thumbnail should be updated.
   virtual bool ShouldAcquirePageThumbnail(const GURL& url) = 0;
 
  protected:
   virtual ~ThumbnailService() {}
 };
 
 }
 
 #endif  // CHROME_BROWSER_THUMBNAILS_THUMBNAIL_SERVICE_H_