[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..17569a13eb470c9f7c71d0be4c27b627e53aaf87
--- /dev/null
+++ b/components/favicon_base/fallback_icon_service.h
@@ -0,0 +1,48 @@
+// 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_
+

[pkotwicz, 2015/01/21 19:44:15]

Nit: Given that eventually you want to make use of FaviconService to determine
the background color, I suggest moving this class to chrome/browser/favicon (I
am fine if you leave the class here and do the move in an upcoming CL when you
want to determine the dominant color from the low res favicon)

[huangs, 2015/01/22 01:13:27]

Leaving the file here.  However, FallbackIconService is supposed to be unaware
of the icon dominant color background color stuff.  For the implicit flow it
will be up to FaviconService to call this.

+#include <vector>

[pkotwicz, 2015/01/21 19:44:15]

#include <string>

[huangs, 2015/01/22 01:13:27]

Done.

+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/task/cancelable_task_tracker.h"
+#include "components/favicon_base/favicon_callback.h"

[pkotwicz, 2015/01/21 19:44:15]

Remove cancelable_task_tracker.h and favicon_callback.h includes

[huangs, 2015/01/22 01:13:27]

Done.

+
+class GURL;
+
+namespace gfx {
+class Canvas;
+}  // namespace gfx

[pkotwicz, 2015/01/21 19:44:15]

Nit: Remove namespace comment. We do not do namespace comments for forward
declarations

[huangs, 2015/01/22 01:13:28]

Done.

+
+namespace favicon_base {
+
+struct FallbackIconStyle;
+
+// 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|).

[pkotwicz, 2015/01/21 19:44:15]

Nits:
- Can you make this method private?
- "a given |canvas|" -> "|canvas|"

Optional: Merge this method with RenderFallbackIconBitmap(). In terms of future
compatibility with bookmark_app_helper.cc, you could have
GetFallbackIconBitmap() which returns a SkBitmap and GetFallbackIconPNGBytes()
which returns raw PNG data.

[huangs, 2015/01/22 01:13:28]

bookmark_app_helper.cc has the comment

// Overlays a shortcut icon over the bottom left corner of a given image.

so I provided this interface. Making it private to the .cc file for now and will
update when this is needed.

+  void DrawFallbackIcon(const GURL& icon_url, int x, int y, int size_in_pixels,
+      const FallbackIconStyle& style, gfx::Canvas* canvas);

[pkotwicz, 2015/01/21 19:44:15]

Style: Each parameter on its own line

[huangs, 2015/01/22 01:13:28]

I thought this is okay if things fit on 2 lines.  Changed anyway.

+
+  // Renders a fallback icon synchronously and returns the bitmap. Returns an
+  // empty std::vector on failure.
+  std::vector<unsigned char> RenderFallbackIconBitmap(
+      const GURL& icon_url, int size_in_pixels, const FallbackIconStyle& style);

[pkotwicz, 2015/01/21 19:44:15]

Style: Each parameter on its own line

[huangs, 2015/01/22 01:13:28]

Done.

+
+ 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_