[wpt] Include revision in wptreport

In this change, `run_wpt_tests` manually adds the commit hash of the
upstream repo in wptreports uploaded to wpt.fyi. The `revision` field
was missing after we stopped using a checked-in version
(crrev.com/c/3842699).

Bug: 1355911
Change-Id: I6c82a97750c64f1d3ff7fbc950200c13c7dbf927
Cq-Include-Trybots: luci.chromium.try:linux-wpt-identity-fyi-rel
Test: From outside chromium/src, run:
Test: run_wpt_tests.py -t Default badging/badge-success.https.html \
Test: --log-wptreport --use-upstream-wpt
Test: jq .run_info.revision out/Default/wpt_reports_chrome.json
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3867910
Commit-Queue: Jonathan Lee <jonathanjlee@google.com>
Reviewed-by: Weizhong Xia <weizhong@google.com>
Cr-Commit-Position: refs/heads/main@{#1041728}
NOKEYCHECK=True
GitOrigin-RevId: d14fe93531aa2ee6aa78e30e36a92e12e5aacf9e

blink/tools/blinkpy/common/checkout/git.py

@@ -201,6 +201,10 @@ def current_branch(self):
             return ''
         return self._branch_from_ref(ref)
 
+    def current_revision(self):
+        """Return the commit hash of HEAD."""
+        return self.run(['rev-parse', 'HEAD']).strip()
+
     def _upstream_branch(self):
         current_branch = self.current_branch()
         return self._branch_from_ref(