Make angle compile on Win64

BUG=http://crbug.com/166496
BUG=http://crbug.com/167187

Landing this for Justin Schuh:
https://codereview.appspot.com/7011048/
Review URL: https://codereview.appspot.com/7040045

git-svn-id: http://angleproject.googlecode.com/svn/trunk@1639 736b8ea6-26fd-11df-bfd4-992fa37f6226