Use hi-resolution favicon variants if available.

chrome/common/icon_messages.h

Index: chrome/common/icon_messages.h
diff --git a/chrome/common/icon_messages.h b/chrome/common/icon_messages.h
index 5f04c94d2816508e044fcf839e29b533bf68a9c1..ed5f1c9a4949f594e26efeaf961ea18d0f29e43a 100644
--- a/chrome/common/icon_messages.h
+++ b/chrome/common/icon_messages.h
@@ -22,14 +22,13 @@ IPC_STRUCT_TRAITS_END()
 
 // Messages sent from the browser to the renderer.
 
-// Requests the renderer to download the specified favicon image encode it as
-// PNG and send the PNG data back ala IconHostMsg_DidDownloadFavicon.
+// Requests the renderer to download the specified favicon image, decode it,
+// and send the image data back via IconHostMsg_DidDownloadFavicon.
 IPC_MESSAGE_ROUTED3(IconMsg_DownloadFavicon,
                     int /* identifier for the request */,
                     GURL /* URL of the image */,
-                    int /* Size of the image. Normally 0, but set if you have
-                           a preferred image size to request, such as when
-                           downloading the favicon */)
+                    int /* Preferred favicon size. Passed on to
+                           IconHostMsg_DidDownloadFavicon, unused otherwise */)
 
 // Messages sent from the renderer to the browser.
 
@@ -38,8 +37,10 @@ IPC_MESSAGE_ROUTED2(IconHostMsg_UpdateFaviconURL,
                     int32 /* page_id */,
                     std::vector<FaviconURL> /* urls of the favicon */)
 
-IPC_MESSAGE_ROUTED4(IconHostMsg_DidDownloadFavicon,
+IPC_MESSAGE_ROUTED5(IconHostMsg_DidDownloadFavicon,
                     int /* Identifier of the request */,
                     GURL /* URL of the image */,
                     bool /* true if there was a network error */,
-                    SkBitmap /* image_data */)
+                    int /* Preferred icon size passed to
+                           IconMsg_DownloadFavicon */,
+                    std::vector<SkBitmap> /* image_data */)