Add metrics to investigate 1% invalid transitions observed during DSE experiment

Bug: 1237951
Change-Id: Ic50fa8e06cf6e4b373a31d0ce328dbd7e194cc56
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3081631


Reviewed-by: Balazs Engedy <engedy@chromium.org>
Reviewed-by: Ravjit Singh Uppal <ravjit@chromium.org>
Commit-Queue: Andy Paicu <andypaicu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#910219}