One MSVC warning and one GCC warning.

I also added a variable to build_angle.gyp that will enforce various rules not normally applied to third party software when built as part of chromium.
Review URL: https://codereview.appspot.com/5570061

git-svn-id: https://angleproject.googlecode.com/svn/trunk@962 736b8ea6-26fd-11df-bfd4-992fa37f6226