[GCM] Add more UMA to GCM

chrome/browser/extensions/api/gcm/gcm_api.cc

Index: chrome/browser/extensions/api/gcm/gcm_api.cc
diff --git a/chrome/browser/extensions/api/gcm/gcm_api.cc b/chrome/browser/extensions/api/gcm/gcm_api.cc
index 343299c6b39b1acb5f224b7e8c9f66dc65134a0f..9134c5ed340fbebdc1dae7bd128f4ec0728000de 100644
--- a/chrome/browser/extensions/api/gcm/gcm_api.cc
+++ b/chrome/browser/extensions/api/gcm/gcm_api.cc
@@ -8,6 +8,7 @@
 #include <map>
 #include <vector>
 
+#include "base/metrics/histogram.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "chrome/browser/profiles/profile.h"
@@ -131,6 +132,8 @@ GcmUnregisterFunction::GcmUnregisterFunction() {}
 GcmUnregisterFunction::~GcmUnregisterFunction() {}
 
 bool GcmUnregisterFunction::DoWork() {
+  UMA_HISTOGRAM_BOOLEAN("GCM.APICallUnregister", true);
+
   GCMProfileService()->Unregister(
       GetExtension()->id(),
       base::Bind(&GcmUnregisterFunction::CompleteFunctionWithResult, this));