The following enums had a small typo causing them to be takend from an
unused block:

EGL_CONTEXT_WEBGL_COMPATIBILITY_ANGLE
EGL_CONTEXT_BIND_GENERATES_RESOURCE_CHROMIUM
EGL_DISPLAY_TEXTURE_SHARE_GROUP_ANGLE

Fix this by temporarily defining a secondary enum. Once Chromium is
fixed upstream we can remove the temporary enum.

Reported by dan.glastonbury@gmail.com.

Bug: angleproject:2806
Change-Id: I2ce1dec0a30d5e83f2bec0ae243fd860cbcea4fc
Reviewed-on: https://chromium-review.googlesource.com/1220371
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>