Enables vertex attrib 0 and assigns a buffer to it

      and makes it impossible to disable.  This makes
most of the tests that were failing pass. The issue
is OpenGL requires attrib 0 to be enabled or it doesn't
render where as OpenGL ES 2.0 does not have this requirement.

A bunch of the conformance tests that were failing were
using only attrib 1.

Since the command buffer can only render with vbos,
no client side buffers, this seems like it works.

TEST=a bunch more conformance tests pass
BUG=none

Review URL: http://codereview.chromium.org/2104004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@47469 0039d316-1c4b-4281-b951-d872f2087c98