Directly iterate over uniforms, not over uniform locations, so we don't waste time looking at locations in the middle of arrays. Gets about 1 fps on a NaCl benchmark.

BUG=
TEST=webgl conformance tests

Review URL: http://codereview.appspot.com/5210042

git-svn-id: https://angleproject.googlecode.com/svn/trunk@792 736b8ea6-26fd-11df-bfd4-992fa37f6226