Add test for Chromium crash when a GPU buffer is deleted

When preserveDrawingBuffer is true and WebGL context leaves a vertex
attribute array != 0 enabled while deleting the buffer attached to that,
Chromium's (at least up to version 33) GPU process will crash when
copying the WebGL drawing buffer. Reproduces at least on NVIDIA OpenGL
drivers.
Add GPU buffer deletion test to test list
Merge pull request #462 from NVIDIA/bufferdata-delete

Add test for Chromium crash when a GPU buffer is deleted