This changes the program query to resolve the link if required. If the
validation layer is skipped the link is resolved in the gl::Context.
Resolving the link on program query allows us to avoid resolving the
link on most of the gl::Program query APIs.

This improves inlining and particularly affects uniform update. It
fixes a performance regression introduced by the parallel shader
linking extension. Gives a 17% increased score on a uniform benchmark.

Also fixes two missing cases of checking for the extension in our
validation code.

Note that some bugs might still exist when the validation layer is
disabled.

Bug: angleproject:2851
Change-Id: I5d725eede3fa147cedf2ce0129791b3412a97a61
Reviewed-on: https://chromium-review.googlesource.com/1255509
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@google.com>