[Fallback Icons] Refactor FallbackIconService to be a BrowserContext-level singleton

components/favicon/core/fallback_icon_service.h

 // Copyright 2015 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 COMPONENTS_FAVICON_CORE_FALLBACK_ICON_SERVICE_H_
 #define COMPONENTS_FAVICON_CORE_FALLBACK_ICON_SERVICE_H_
 
-#include <string>
 #include <vector>
 
 #include "base/macros.h"
+#include "components/keyed_service/core/keyed_service.h"
 
+class FallbackIconClient;
 class GURL;
 
 namespace gfx {
 class Canvas;
 }
 
 namespace favicon_base {
 struct FallbackIconStyle;
 }
 
 // A service to provide methods to render fallback favicons.
-class FallbackIconService {
+class FallbackIconService : public KeyedService {
  public:
-  explicit FallbackIconService(const std::vector<std::string>& font_list);
-  ~FallbackIconService();
+  explicit FallbackIconService(FallbackIconClient* fallback_icon_client);
+  ~FallbackIconService() override;
 
   // Renders a fallback icon synchronously and returns the bitmap. Returns an
   // empty std::vector on failure. |size| is icon width and height in pixels.
   std::vector<unsigned char> RenderFallbackIconBitmap(
       const GURL& icon_url,
       int size,
       const favicon_base::FallbackIconStyle& style);
 
  private:
   // Renders a fallback icon on |canvas| at position (|x|, |y|). |size| is icon
   // width and height in pixels.
   void DrawFallbackIcon(const GURL& icon_url,
                         int size,
                         const favicon_base::FallbackIconStyle& style,
                         gfx::Canvas* canvas);
 
-  std::vector<std::string> font_list_;
+  FallbackIconClient* fallback_icon_client_;
 
   DISALLOW_COPY_AND_ASSIGN(FallbackIconService);
 };
 
 #endif  // COMPONENTS_FAVICON_CORE_FALLBACK_ICON_SERVICE_H_