[Sync] SyncEngine refactor part 1: interfaces.

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 8ddf95ea8c71cfbf083369e042291f04ff0d513d..e164d7bccada7c4c5be4d34c4b1e37c0907f650c 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -65507,7 +65507,7 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <owner>zea@chromium.org</owner>
   <summary>
     Time taken from the start of sync shutdown (in ProfileSyncService) until the
-    backend (SyncBackendHost) is fully destroyed.
+    backend (SyncEngine) is fully destroyed.
   </summary>
 </histogram>
 
@@ -65545,7 +65545,7 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <owner>jeremy@chromium.org</owner>
   <owner>zea@google.com</owner>
   <summary>
-    Time spent after ProfileSyncService *creation* but before SyncBackendHost
+    Time spent after ProfileSyncService *creation* but before SyncEngine
     initialization.
   </summary>
 </histogram>
@@ -65554,7 +65554,7 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <owner>jeremy@chromium.org</owner>
   <owner>zea@google.com</owner>
   <summary>
-    Time spent after ProfileSyncService *creation* but before SyncBackendHost
+    Time spent after ProfileSyncService *creation* but before SyncEngine
     initialization.
   </summary>
 </histogram>