roll skia to 4500

Review URL: https://chromiumcodereview.appspot.com/10689135

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@145886 0039d316-1c4b-4281-b951-d872f2087c98

DEPS

@@ -57,7 +57,7 @@ vars = {
   "ffmpeg_hash": "23f177366e3bce3a628a7d3feedceed4e18dcc04",
 
   "sfntly_revision": "134",
-  "skia_revision": "4480",
+  "skia_revision": "4500",
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling Skia
   # and V8 without interference from each other.