Drop -{webkit,moz}-box-shadow

* The last version of Firefox to require the 'moz' prefix was 3.6, 25(!)
  versions ago.
* Most recent versions of WebKit that require the vendor prefix: Chrome 9,
  Safari 5.0, iOS Safari 4.3, Android 3.0.

Change-Id: If0c484444ef9db2f5435193cfe7a2e445862e956
Merge "Drop -{webkit,moz}-box-shadow"