No functional change. When we trigger a capture at frame X, the value
of X is not important. Instead we'll record the frames as 1,2,3,etc.
Helps keep the traces more consistent and re-trace the same way as
they are captured.

Bug: angleproject:5134
Change-Id: Icd8654d509423edcc74cd0ef694795a787f5cc05
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2500602
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Cody Northrop <cnorthrop@google.com>
Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>