Prefixing internal names will avoid clashes with user-defined names.
We use prefix webgl_angle_ so that the internal names are both
reserved in WebGL on one hand and clearly separated from hashed names
starting with just webgl_ on the other hand.

BUG=angleproject:1597
TEST=WebGL conformance tests

Change-Id: I7deef9c1a38105c8b57eda13c84eec13e515a91a
Reviewed-on: https://chromium-review.googlesource.com/406247Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>