Protect the kGoogleServicesUsername pref.

Also add missing items in the TrackedPreference histograms enum.
(and clean up histogram labels to exclude namespaces)

BUG=438105
TEST=
A) First launch of Chrome with this change should result in a Settings.TrackedPreferenceTrustedInitialized for pref 21.
B) Tampering with google.services.username in Secure Preferences while Chrome isn't running results in the user being signed out on the next launch.

Review URL: https://codereview.chromium.org/775483004

Cr-Commit-Position: refs/heads/master@{#306444}

2 files changed, 28 insertions, 19 deletions

diff --git a/chrome/browser/prefs/chrome_pref_service_factory.cc b/chrome/browser/prefs/chrome_pref_service_factory.cc
index 865864f..38251e6 100644
--- a/chrome/browser/prefs/chrome_pref_service_factory.cc
+++ b/chrome/browser/prefs/chrome_pref_service_factory.cc
@@ -198,6 +198,13 @@ const PrefHashFilter::TrackedPreferenceMetadata kTrackedPrefs[] = {
     PrefHashFilter::TRACKING_STRATEGY_ATOMIC
   },
 #endif
+  {
+    21, prefs::kGoogleServicesUsername,
+    PrefHashFilter::ENFORCE_ON_LOAD,
+    PrefHashFilter::TRACKING_STRATEGY_ATOMIC
+  },
+  // See note at top, new items added here also need to be added to
+  // histograms.xml's TrackedPreference enum.
 };
 
 // One more than the last tracked preferences ID above.
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index f46a8b8..e22ab98 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -56317,26 +56317,28 @@ To add a new entry, add it with any value and run test to compute valid value.
 </enum>
 
 <enum name="TrackedPreference" type="int">
-  <int value="0" label="prefs::kShowHomeButton"/>
-  <int value="1" label="prefs::kHomePageIsNewTabPage"/>
-  <int value="2" label="prefs::kHomePage"/>
-  <int value="3" label="prefs::kRestoreOnStartup"/>
-  <int value="4" label="prefs::kURLsToRestoreOnStartup"/>
+  <int value="0" label="kShowHomeButton"/>
+  <int value="1" label="kHomePageIsNewTabPage"/>
+  <int value="2" label="kHomePage"/>
+  <int value="3" label="kRestoreOnStartup"/>
+  <int value="4" label="kURLsToRestoreOnStartup"/>
   <int value="5" label="extensions::pref_names::kExtensions"/>
-  <int value="6" label="prefs::kGoogleServicesLastUsername"/>
-  <int value="7" label="prefs::kSearchProviderOverrides"/>
-  <int value="8" label="prefs::kDefaultSearchProviderSearchURL"/>
-  <int value="9" label="prefs::kDefaultSearchProviderKeyword"/>
-  <int value="10" label="prefs::kDefaultSearchProviderName"/>
-  <int value="11" label="prefs::kPinnedTabs"/>
-  <int value="12"
-      label="extensions::pref_names::kKnownDisabled (Obsolete 07/2014)"/>
-  <int value="13" label="prefs::kProfileResetPromptMemento"/>
-  <int value="14"
-      label="DefaultSearchManager::kDefaultSearchProviderDataPrefName"/>
-  <int value="15" label="prefs::kPreferenceResetTime"/>
-  <int value="16" label="prefs::kSafeBrowsingIncidentReportSent"/>
-  <int value="17" label="sync_driver::prefs::kSyncRemainingRollbackTries"/>
+  <int value="6" label="kGoogleServicesLastUsername"/>
+  <int value="7" label="kSearchProviderOverrides"/>
+  <int value="8" label="kDefaultSearchProviderSearchURL"/>
+  <int value="9" label="kDefaultSearchProviderKeyword"/>
+  <int value="10" label="kDefaultSearchProviderName"/>
+  <int value="11" label="kPinnedTabs"/>
+  <int value="12" label="kKnownDisabled (Obsolete 07/2014)"/>
+  <int value="13" label="kProfileResetPromptMemento"/>
+  <int value="14" label="kDefaultSearchProviderDataPrefName"/>
+  <int value="15" label="kPreferenceResetTime"/>
+  <int value="16" label="kSafeBrowsingIncidentReportSent"/>
+  <int value="17" label="kSyncRemainingRollbackTries"/>
+  <int value="18" label="kSafeBrowsingIncidentsSent"/>
+  <int value="19" label="kSwReporterPromptVersion"/>
+  <int value="20" label="kSwReporterPromptReason"/>
+  <int value="21" label="kGoogleServicesUsername"/>
 </enum>
 
 <enum name="TranslateError" type="int">