This commit adds angle-based validation and translation to WebGL
shaders.
The changes to the tex_image_2d test is neccessary (it was not valid
GLES 2.0 shader language).
This commit implements WebGL's:
* cullFace
* frontFace
* enable
* disable
* depthMask
* colorMask
* clearDepth
* clearStencil
* depthFunc
* depthRange
* hint
* lineWidth
* pixelStorei
* polygonOffset
* texParameteri
* texParameterf
* texImage2D (partially)
It inlines a lot of OpenGL calls to keep the file
`components/canvas/webgl_paint_task.rs` as small as possible while
keeping readability.
It also improves error detection on previous calls, and sets node damage
on the canvas in the drawing calls.
It adds a `TexImage2D` reftest, even though it's not enabled because:
* WebGL paints the image when it loads (asynchronously), so the reftest doesn't wait for it and it finishes early
* If we change the source for the base64 src of the image it works as expected in non-headless mode, but the test harness locks
