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Currently EglThreadContext only creates OpenGL ES 2 context. OpenGL ES 3 is
backward compatible with ES 2 and has new interfaces (e.g. GL_PACK_ROW_LENGTH)
that can improve the performance of the client OpenGL renderer.

This CL makes EglThreadContext create OpenGL ES context of the highest
version supported by the software or hardward of the device.

BUG=385924

Review-Url: https://codereview.chromium.org/2175913002
Cr-Commit-Position: refs/heads/master@{#407589}