Fixed gl_FragCoord emulation for point sprites of size > 1 using VPOS semantic for x and y coordinates rather than previous per-vertex emulation when running on Shader Model 3. Verified fix in Chromium with test case from bug. BUG=http://code.google.com/p/angleproject/issues/detail?id=71 TEST=test case from bug TBR=nicolas (LGTM'd by dgkoch) Review URL: http://codereview.appspot.com/2921041 git-svn-id: https://angleproject.googlecode.com/svn/trunk@473 736b8ea6-26fd-11df-bfd4-992fa37f6226