Add test to ensure that doing texImage2D from a WebGL canvas works.
Merge pull request #132 from jbauman2/webglcanvastest

Add test to ensure that doing texImage2D from a WebGL canvas works.
Hook up jbauman's new test conformance/textures/tex-image-webgl.html.
Merge pull request #133 from kenrussell/addtest

Hook up jbauman's new test conformance/textures/tex-image-webgl.html.