[Favicon] Add new fallback icon rendering flow.

components/favicon_base/favicon_types.h

 // Copyright 2014 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_TYPES_H_
 #define COMPONENTS_FAVICON_BASE_FAVICON_TYPES_H_
 
 #include "base/memory/ref_counted_memory.h"
+#include "ui/gfx/color_utils.h"
 #include "ui/gfx/geometry/size.h"
 #include "ui/gfx/image/image.h"
 #include "url/gurl.h"
 
 namespace favicon_base {
 
 typedef int64 FaviconID;
 
 // Defines the icon types. They are also stored in icon_type field of favicons
 // table.
@@ skipping 46 matching lines @@
   GURL icon_url;
 
   // The icon type of the containing favicon.
   IconType icon_type;
 };
 
 // Define type with same structure as FaviconRawBitmapResult for passing data to
 // HistoryBackend::SetFavicons().
 typedef FaviconRawBitmapResult FaviconRawBitmapData;
 
+// Rendering specifications of a fallback icon, which is a square image as a
+// solid rounded rectangle containing a single letter. The specs exclude icon
+// URL and size, since these are only specified when we render.
+struct FallbackIconSpecs {
+  FallbackIconSpecs();
+  ~FallbackIconSpecs();
+
+  // Icon background fill color.
+  SkColor background_color;
+
+  // Icon text color.
+  SkColor text_color;
+
+  // Ratio in [0.0, 1.0] from text font size (pixels) to icon size.
+  double font_size_ratio;
+
+  // Ratio in [0.0, 0.5] from rounded square's corner radius to square size.
+  // In particular, 0.0 => square and 0.5 => circle.
+  double corner_radius_ratio;

[pkotwicz, 2015/01/19 04:32:02]

I think that a pixel corner radius is more intuitive (Alternatively you can
rename this member to "roundness". 0.0f -> square, 1.0f -> circle)

[huangs, 2015/01/20 22:20:41]

"Roundness" is a good idea, updating.

+
+  // If any field change, need to update FallbackIconSpecsBuilder.
+};
+
 }  // namespace favicon_base
 
 #endif  // COMPONENTS_FAVICON_BASE_FAVICON_TYPES_H_