[Sync] Add favicon datatype proto support

sync/protocol/favicon_image_specifics.proto

+// Copyright (c) 2012 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.
+//
+// Sync protocol datatype extension for the favicon image specifics.
+
+syntax = "proto2";
+
+option optimize_for = LITE_RUNTIME;
+option retain_unknown_fields = true;
+
+package sync_pb;
+
+message FaviconData {
+  // The image data for the favicon (PNG encoded).
+  optional bytes favicon = 1;
+  // The favicon dimensions.
+  optional int32 width = 2;
+  optional int32 height = 3;
+}
+
+// Image data for favicons. Multiple resolutions are supported.
+message FaviconImageSpecifics {
+  // The url of the favicon image.
+  optional string favicon_url = 1;
+
+  // The favicons associated with this source, one per scale type.
+  // Favicons images should be stored into the field that best corresponds to
+  // their scale. If multiple favicons are appropriate, the highest resolution
+  // that doesn't violate the maximum should be stored.
+
+  // A normal low-resolution web favicon (max resolution 16x16).
+  optional FaviconData favicon_web = 2;
+  // A slightly higher-resolution web favicon (max resolution 32x32).
+  optional FaviconData favicon_web_32 = 3;
+  // A high-resolution touch favicon (not precomposed, max resolution 64x64).
+  optional FaviconData favicon_touch_64 = 4;
+  // A high-resolution touch favicon (precomposed, max resolution 64x64).
+  optional FaviconData favicon_touch_precomposed_64 = 5;
+}