Extract renderer-side favicon downloading code into separate helper class

chrome/renderer/favicon_helper.h

Index: chrome/renderer/favicon_helper.h
diff --git a/chrome/renderer/favicon_helper.h b/chrome/renderer/favicon_helper.h
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index 0000000000000000000000000000000000000000..aeccd28a804497a88616f41d2a6898aa9a764579
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+++ b/chrome/renderer/favicon_helper.h
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+// Copyright (c) 2011 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_RENDERER_FAVICON_HELPER_H_
+#define CHROME_RENDERER_FAVICON_HELPER_H_
+
+#include <string>
+#include <vector>
+
+#include "base/memory/linked_ptr.h"
+#include "base/memory/scoped_vector.h"
+#include "content/public/renderer/render_view_observer.h"
+#include "googleurl/src/gurl.h"
+
+struct FaviconURL;
+class SkBitmap;
+
+namespace webkit_glue {
+class MultiResolutionImageResourceFetcher;
+}
+
+// This class deals with favicon downloading.
+// There is one FaviconHelper per RenderView, which is owned by the RenderView.
+class FaviconHelper : public content::RenderViewObserver {
+ public:
+  explicit FaviconHelper(content::RenderView* render_view);
+
+ private:
+  virtual ~FaviconHelper();
+
+  // Message handler.
+  void OnDownloadFavicon(int id, const GURL& image_url, int image_size);
+
+  // Requests to download a favicon image. When done, the RenderView
+  // is notified by way of DidDownloadFavicon. Returns true if the
+  // request was successfully started, false otherwise. id is used to
+  // uniquely identify the request and passed back to the
+  // DidDownloadFavicon method. If the image has multiple frames, the
+  // frame whose size is image_size is returned. If the image doesn't
+  // have a frame at the specified size, the first is returned.
+  bool DownloadFavicon(int id, const GURL& image_url, int image_size);
+
+  // This callback is triggered when DownloadFavicon completes, either
+  // succesfully or with a failure. See DownloadFavicon for more
+  // details.
+  void DidDownloadFavicon(
+      int requested_size,
+      webkit_glue::MultiResolutionImageResourceFetcher* fetcher,
+      const std::vector<SkBitmap>& images);
+
+  // Decodes a data: URL image or returns an empty image in case of failure.
+  SkBitmap ImageFromDataUrl(const GURL&) const;
+
+  // Send a message to update the favicon URL for a page.
+  void SendUpdateFaviconURL(int32 routing_id,
+                            int32 page_id,
+                            const std::vector<FaviconURL>& urls);
+
+  // RenderViewObserver implementation.
+  virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
+  virtual void DidStopLoading() OVERRIDE;
+  virtual void DidChangeIcon(WebKit::WebFrame* frame,
+                             WebKit::WebIconURL::Type icon_type) OVERRIDE;
+
+  typedef ScopedVector<webkit_glue::MultiResolutionImageResourceFetcher>
+    ImageResourceFetcherList;
+
+  // ImageResourceFetchers schedule via DownloadImage.
+  ImageResourceFetcherList image_fetchers_;
+
+  DISALLOW_COPY_AND_ASSIGN(FaviconHelper);
+};
+
+#endif  // CHROME_RENDERER_FAVICON_HELPER_H_