[Favicon] Add new fallback icon rendering flow.

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
new file mode 100644
index 0000000000000000000000000000000000000000..05f8cce757d7a4536f21be105ca4124374ac1105
--- /dev/null
+++ b/components/favicon_base/fallback_icon_service.h
@@ -0,0 +1,51 @@
+// 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_BASE_FAVICON_FALLBACK_ICON_SERVICE_H_
+#define COMPONENTS_FAVICON_BASE_FAVICON_FALLBACK_ICON_SERVICE_H_

[stevenjb, 2015/01/29 21:41:08]

extra _FAVICON_

[huangs, 2015/01/29 23:48:27]

Done.

+
+#include <string>
+#include <vector>
+
+#include "base/macros.h"
+
+class GURL;
+
+namespace gfx {
+class Canvas;
+}
+
+namespace favicon_base {
+
+struct FallbackIconStyle;
+
+// A service to provide methods to render fallback favicons.
+class FallbackIconService {
+ public:
+  FallbackIconService();
+  ~FallbackIconService();
+
+  // Renders a fallback icon synchronously and returns the bitmap. Returns an
+  // empty std::vector on failure. |size| is in pixels.

[stevenjb, 2015/01/29 21:41:08]

Could you explain what exactly |size| refers to?

[huangs, 2015/01/29 23:48:27]

Done.

+  std::vector<unsigned char> RenderFallbackIconBitmap(
+      const GURL& icon_url,
+      int size,
+      const FallbackIconStyle& style);
+
+ private:
+  // Renders a fallback icon on |canvas| at position (|x|, |y|). |size| is in
+  // pixels.
+  void DrawFallbackIcon(const GURL& icon_url,
+                        int size,
+                        const FallbackIconStyle& style,
+                        gfx::Canvas* canvas);
+
+  std::vector<std::string> fallback_icon_font_list_;;
+
+  DISALLOW_COPY_AND_ASSIGN(FallbackIconService);
+};
+
+}  // namespace favicon_base
+
+#endif  // COMPONENTS_FAVICON_BASE_FAVICON_FALLBACK_ICON_SERVICE_H_