[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
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index 0000000000000000000000000000000000000000..dc45db4b864e2d830fa3b7b42e76a5cabe52a1aa
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+++ b/components/favicon_base/fallback_icon_service.h
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+// 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_
+
+#include <vector>
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/task/cancelable_task_tracker.h"
+#include "components/favicon_base/favicon_callback.h"
+
+class GURL;
+
+namespace gfx {
+class Canvas;
+}  // namespace gfx
+
+namespace favicon_base {
+
+struct FallbackIconSpecs;
+
+// A service to provide methods to render fallback favicons.
+class FallbackIconService {
+ public:
+  FallbackIconService();
+  ~FallbackIconService();
+
+  // Renders a fallback icon on a given |canvas| at position (|x|, |y|).
+  void DrawFallbackIcon(const GURL& icon_url, int x, int y, int size_in_pixels,
+      const FallbackIconSpecs& specs, gfx::Canvas* canvas);
+
+  // Returns a fallback icon bitmap via callback. Used by FaviconService.
+  base::CancelableTaskTracker::TaskId GetFallbackIcon(
+      const GURL& icon_url,
+      int size_in_pixels,
+      const FallbackIconSpecs& specs,
+      const FaviconResultsCallback& callback,
+      base::CancelableTaskTracker* tracker);
+
+ private:
+  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_