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

components/favicon_base/fallback_icon_service.h

Index: components/favicon_base/fallback_icon_service.h
diff --git a/components/favicon_base/fallback_icon_service.h b/components/favicon_base/fallback_icon_service.h
index cc98adfe20feb677029bfa6c6cd3b010f38045c3..b737f786e7cc4eeea882d55c5227b44d6f52762d 100644
--- a/components/favicon_base/fallback_icon_service.h
+++ b/components/favicon_base/fallback_icon_service.h
@@ -5,11 +5,12 @@
 #ifndef COMPONENTS_FAVICON_BASE_FALLBACK_ICON_SERVICE_H_
 #define COMPONENTS_FAVICON_BASE_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 {
@@ -21,9 +22,9 @@ 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);
+  explicit FallbackIconService(FallbackIconClient* fallback_icon_client);
   ~FallbackIconService();
 
   // Renders a fallback icon synchronously and returns the bitmap. Returns an
@@ -41,7 +42,7 @@ class FallbackIconService {
                         const FallbackIconStyle& style,
                         gfx::Canvas* canvas);
 
-  std::vector<std::string> font_list_;
+  FallbackIconClient* fallback_icon_client_;
 
   DISALLOW_COPY_AND_ASSIGN(FallbackIconService);
 };