Fix GPU Tracing offset calculation.
I found every once in awhile the offset on android would be wrong for a
trace, I tracked it down to occasionally between the time we calculate
the offset and begin the trace the GPU will reset the timing. Moving
the offset calculation until after we start the query fixes this
issue.
R=dcastagna@chromium.org, vmiura@chromium.org
BUG=None
TEST=local tracing 5 times and didn't see the offset calculation wrong.
Review URL: https://codereview.chromium.org/
924533005
Cr-Commit-Position: refs/heads/master@{#316129}