Reland: Verify shader link correctness after looking up in program cache Since the program cache takes shader sources into account, if the cache is hit the shaders should have been correct for link. Bug: angleproject:8297 Change-Id: Iccadc63a976689d7fa06d0a5ccfe81a594c424e8 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5003236 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Charlie Lao <cclao@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>