This patch parse the sizes attribute into vector of IntSize, also added sizes in WebIconURL, so it could be used by chromium 

BUG=349039

Review URL: https://codereview.chromium.org/196743002

git-svn-id: svn://svn.chromium.org/blink/trunk@169404 bbb929c8-8fbe-4397-9dbb-9b2b20218538