CL https://chromium-review.googlesource.com/c/575785/

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7faa001ae37d006dd3c4b71c55513888342da8c0

commit 7faa001ae37d006dd3c4b71c55513888342da8c0
Author: Jeff Carpenter <jeffcarp@chromium.org>
Date: Tue Jul 18 22:57:47 2017

[WPT Export] Favor Change-Id over Commit-Position when finding PRs

From time to time the exporter is unable to find and merge an upstream PR
once its been landed. This is caused by the exporter first searching by
Commit-Position, which in the case of a landed commit does not correspond
to what's on the PR. However, this can lead to false positives where the
Commit-Position in a commit points to another, unrelated upstream PR. This
change fixes that problem by first looking for PRs by Change-Id, which never
changes.

Bug:  745880 
Change-Id: I36b12a486fcfce9190ef8d2a9320b723b359ba9b
Reviewed-on: https://chromium-review.googlesource.com/575785
Commit-Queue: Jeff Carpenter <jeffcarp@chromium.org>
Reviewed-by: Quinten Yearsley <qyearsley@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487646}
[modify] https://crrev.com/7faa001ae37d006dd3c4b71c55513888342da8c0/third_party/WebKit/Tools/Scripts/webkitpy/w3c/test_exporter.py
[modify] https://crrev.com/7faa001ae37d006dd3c4b71c55513888342da8c0/third_party/WebKit/Tools/Scripts/webkitpy/w3c/test_exporter_unittest.py

Going to close this for now. Will reopen if we observe this again.

SGTM -- I suspect it's probably solved now :-)