Optimize some operations for float type in texture format conversions of WebGL
https://bugs.webkit.org/show_bug.cgi?id=107526

Patch by Jun Jiang <jun.a.jiang@intel.com> on 2013-02-02
Reviewed by Darin Adler.

Some small changes are made to optimize the operations for float type in the texture format conversion of WebGL to improve performance.

Already covered by current tests.

* platform/graphics/GraphicsContext3D.cpp:
(WebCore):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@141706 268f45cc-cd09-0410-ab3c-d52691b4dbfc