Add a UMA to measure RTT in registering "origin" path.

BUG=None
TEST=Manually
R=asvitkine@chromium.org, tzik@chromium.org

Review URL: https://codereview.chromium.org/269343008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@269527 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/sync_file_system/drive_backend/sync_engine.cc

@@ -7,7 +7,9 @@
 #include <vector>
 
 #include "base/bind.h"
+#include "base/metrics/histogram.h"
 #include "base/threading/sequenced_worker_pool.h"
+#include "base/time/time.h"
 #include "base/values.h"
 #include "chrome/browser/drive/drive_api_service.h"
 #include "chrome/browser/drive/drive_notification_manager.h"
@@ -108,6 +110,14 @@ namespace {
 
 void EmptyStatusCallback(SyncStatusCode status) {}
 
+void DidRegisterOrigin(const base::TimeTicks& start_time,
+                       const SyncStatusCallback& callback,
+                       SyncStatusCode status) {
+  base::TimeDelta delta(base::TimeTicks::Now() - start_time);
+  HISTOGRAM_TIMES("SyncFileSystem.RegisterOriginTime", delta);
+  callback.Run(status);
+}
+
 }  // namespace
 
 scoped_ptr<SyncEngine> SyncEngine::CreateForBrowserContext(
@@ -247,7 +257,10 @@ void SyncEngine::RegisterOrigin(
                  base::Unretained(sync_worker_.get()),
                  origin,
                  RelayCallbackToCurrentThread(
-                     FROM_HERE, callback)));
+                     FROM_HERE,
+                     base::Bind(&DidRegisterOrigin,
+                                base::TimeTicks::Now(),
+                                callback))));
 }
 
 void SyncEngine::EnableOrigin(

tools/metrics/histograms/histograms.xml

@@ -27956,6 +27956,15 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="SyncFileSystem.RegisterOriginTime" units="milliseconds">
+  <owner>peria@chromium.org</owner>
+  <owner>tzik@chromium.org</owner>
+  <summary>
+    Time elapsed to register a Chrome App to SyncFilesystem. Recorded for each
+    registration request by apps.
+  </summary>
+</histogram>
+
 <histogram name="SyncFileSystem.TrackerNumber">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>