Add histograms to the rendez-vous process (ProcessSingleton).

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 d63ce4fb107396f4917f1c3e2bcfda6e488cde6e..4236e785ec64345fb49a5f1b1512bca6751951eb 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -5652,6 +5652,39 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Chrome.ProcessSingleton.NotifyResult" enum="NotifyResult">
+  <owner>gab@chromium.org</owner>
+  <summary>
+    The result of every rendez-vous reported once per browser process launch.
+  </summary>
+</histogram>
+
+<histogram name="Chrome.ProcessSingleton.TimeToCreate" units="ms">
+  <owner>gab@chromium.org</owner>
+  <summary>
+    Time it takes to grab the process singleton. Reported once per successful
+    attempt at obtaining the singleton.
+  </summary>
+</histogram>
+
+<histogram name="Chrome.ProcessSingleton.TimeToFailure" units="ms">
+  <owner>gab@chromium.org</owner>
+  <summary>
+    Time it takes to return an error from the process singleton algorithm (nor
+    succeeding in obtaining it, nor in generating a rendez-vous). This does not
+    include time spent in the fast notification path (chrome_exe_main_win.cc).
+  </summary>
+</histogram>
+
+<histogram name="Chrome.ProcessSingleton.TimeToNotify" units="ms">
+  <owner>gab@chromium.org</owner>
+  <summary>
+    Time it takes to find the process singleton owner and notify it. Reported
+    once per successful rendez-vous. This does not include time spent in the
+    fast notification path (chrome_exe_main_win.cc).
+  </summary>
+</histogram>
+
 <histogram name="Chrome.SearchSelectExempt" enum="SearchEngine">
   <obsolete>
     Deprecated 8/2013. No longer tracked.
@@ -91137,6 +91170,13 @@ value.
   <int value="6" label="Invalid Argument error"/>
 </enum>
 
+<enum name="NotifyResult" type="int">
+  <int value="0" label="PROCESS_NONE"/>
+  <int value="1" label="PROCESS_NOTIFIED"/>
+  <int value="2" label="PROFILE_IN_USE"/>
+  <int value="3" label="LOCK_ERROR"/>
+</enum>
+
 <enum name="NotStreamingReason" type="int">
   <int value="0" label="Already loaded"/>
   <int value="1" label="Not HTTP"/>