Clarify that histogram owners should be Googlers

Specify in the histogram README and presubmit checks that the primary
owner of a histogram needs to be a Googler, not just someone with an
@chromium.org email address.

Bug: 1142896
Change-Id: I39e522430d6cacb44c39645efb31499394e8d218
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2504631
Commit-Queue: Mario Bianucci <mabian@microsoft.com>
Reviewed-by: Dirk Pranke <dpranke@google.com>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#821780}

tools/metrics/histograms/README.md

@@ -500,7 +500,7 @@ contact for any questions or maintenance tasks, such as extending a histogram's
 expiry or deprecating the metric.
 
 Histograms must have a primary owner and may have secondary owners. A primary
-owner is an individual with an @chromium.org or @google.com email address, e.g.
+owner is a Googler with an @google.com or @chromium.org email address, e.g.
 <owner>lucy@chromium.org</owner>, who is ultimately responsible for maintaining
 the metric. Secondary owners may be other individuals, team mailing lists, e.g.
 <owner>my-team@google.com</owner>, or paths to OWNERS files, e.g.

tools/metrics/histograms/expand_owners.py

@@ -79,7 +79,7 @@ def _IsEmailOrPlaceholder(is_first_owner, owner_tag_text, histogram_name,
   if should_check_owner_email and not _IsValidPrimaryOwnerEmail(owner_tag_text):
     raise Error(
         'The histogram {} must have a valid primary owner, i.e. a '
-        'person with an @google.com or @chromium.org email address.'.format(
+        'Googler with an @google.com or @chromium.org email address.'.format(
             histogram_name))
 
   return is_email or is_placeholder

tools/metrics/histograms/expand_owners_unittest.py

@@ -383,7 +383,7 @@ class ExpandOwnersTest(unittest.TestCase):
     with self.assertRaisesRegexp(
         expand_owners.Error,
         'The histogram Caffeination must have a valid primary owner, i.e. a '
-        'person with an @google.com or @chromium.org email address.'):
+        'Googler with an @google.com or @chromium.org email address.'):
       expand_owners.ExpandHistogramsOWNERS(histograms_without_valid_first_owner)
 
   def testExpandOwnersWithoutValidPrimaryOwner_TeamEmail(self):
@@ -406,7 +406,7 @@ class ExpandOwnersTest(unittest.TestCase):
     with self.assertRaisesRegexp(
         expand_owners.Error,
         'The histogram Caffeination must have a valid primary owner, i.e. a '
-        'person with an @google.com or @chromium.org email address.'):
+        'Googler with an @google.com or @chromium.org email address.'):
       expand_owners.ExpandHistogramsOWNERS(histograms_without_valid_first_owner)
 
   def testExpandOwnersWithoutValidPrimaryOwner_InvalidEmail(self):
@@ -429,7 +429,7 @@ class ExpandOwnersTest(unittest.TestCase):
     with self.assertRaisesRegexp(
         expand_owners.Error,
         'The histogram Caffeination must have a valid primary owner, i.e. a '
-        'person with an @google.com or @chromium.org email address.'):
+        'Googler with an @google.com or @chromium.org email address.'):
       expand_owners.ExpandHistogramsOWNERS(histograms_without_valid_first_owner)
 
   def testExpandOwnersWithFakeFilePath(self):