Testing shows that using timestamp queries and deferring the
query get calls until after the frame produces little overhead.
Also this fixes a missing GPU time reset between iterations.

Bug: angleproject:4879
Change-Id: I2a566548add1536aab689cd969594a15f0628da3
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2321573Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Cody Northrop <cnorthrop@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>