Fixes issue that if we don't simulate a disabled vertex attrib 0 (as in the case of running on top of OpenGL ES 2.0 or ANGLE) then we actually have to disable it.
Fixes issue that if we don't simulate a disabled
vertex attrib 0 (as in the case of running on top
of OpenGL ES 2.0 or ANGLE) then we actually have
to disable it.

TEST=updated webgl conformance tests.
BUG=71960

Review URL: http://codereview.chromium.org/6456016

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@74323 0039d316-1c4b-4281-b951-d872f2087c98

ropik/chromium,yitian134/chromium,ropik/chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,ropik/chromium,ropik/chromium,adobe/chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,yitian134/chromium,adobe/chromium,adobe/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,gavinp/chromium,gavinp/chromium,yitian134/chromium,yitian134/chromium,gavinp/chromium,yitian134/chromium,gavinp/chromium,ropik/chromium,ropik/chromium,yitian134/chromium,adobe/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,adobe/chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,yitian134/chromium,gavinp/chromium,gavinp/chromium,gavinp/chromium,adobe/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,ropik/chromium,gavinp/chromium,ropik/chromium,ropik/chromium,gavinp/chromium,adobe/chromium,yitian134/chromium,Crystalnix/house-of-life-chromium,adobe/chromium