TRex invalidates depth but doesn't disable depth before the render
pass ends.  The render pass isn't ended, but a storeOp of STORE was
used instead of DONT_CARE, which causes a performance regression.

Bug: b/163854287
Change-Id: Iebd9999ef66c11ff334db3eef2943f58eb2d5053
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2377105Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Charlie Lao <cclao@google.com>
Commit-Queue: Ian Elliott <ianelliott@google.com>