Add UMA for policy load result of enrolled Chrome OS devices.

chrome/browser/chromeos/policy/device_cloud_policy_store_chromeos.cc

Index: chrome/browser/chromeos/policy/device_cloud_policy_store_chromeos.cc
diff --git a/chrome/browser/chromeos/policy/device_cloud_policy_store_chromeos.cc b/chrome/browser/chromeos/policy/device_cloud_policy_store_chromeos.cc
index 70434098c7126d4cd19a96481ec20ce40a8064a6..b0b0c581caed68c581c426202fc63f0307e575a0 100644
--- a/chrome/browser/chromeos/policy/device_cloud_policy_store_chromeos.cc
+++ b/chrome/browser/chromeos/policy/device_cloud_policy_store_chromeos.cc
@@ -5,6 +5,7 @@
 #include "chrome/browser/chromeos/policy/device_cloud_policy_store_chromeos.h"
 
 #include "base/bind.h"
+#include "base/metrics/sparse_histogram.h"
 #include "base/sequenced_task_runner.h"
 #include "chrome/browser/chromeos/policy/device_policy_decoder_chromeos.h"
 #include "chrome/browser/chromeos/policy/enterprise_install_attributes.h"
@@ -22,6 +23,7 @@ DeviceCloudPolicyStoreChromeOS::DeviceCloudPolicyStoreChromeOS(
     : device_settings_service_(device_settings_service),
       install_attributes_(install_attributes),
       background_task_runner_(background_task_runner),
+      uma_done_(false),
       weak_factory_(this) {
   device_settings_service_->AddObserver(this);
 }
@@ -133,6 +135,20 @@ void DeviceCloudPolicyStoreChromeOS::UpdateFromService() {
     return;
   }
 
+  // Fill UMA histogram once per session.  Skip temp validation error because it
+  // is not a definitive result (policy load will be retried).
+  const chromeos::DeviceSettingsService::Status status =
+      device_settings_service_->status();
+  if (!uma_done_ &&
+      status != chromeos::DeviceSettingsService::STORE_TEMP_VALIDATION_ERROR) {
+    uma_done_ = true;
+    UMA_HISTOGRAM_SPARSE_SLOWLY(
+        "Enterprise.EnrolledPolicyHasDMToken",

[Alexei Svitkine (slow), 2014/05/26 17:27:11]

This looks like a boolean histogram, so there's no need for it to be sparse. Use
UMA_HISTOGRAM_BOOLEAN instead.

[Thiemo Nagel, 2014/05/26 17:54:30]

Thanks for catching this!  I had started with a more complex histogram and
simplified it until there were only two bins left...

+        status == chromeos::DeviceSettingsService::STORE_SUCCESS &&
+        device_settings_service_->policy_data() &&
+        !device_settings_service_->policy_data()->has_request_token());

[Alexei Svitkine (slow), 2014/05/26 17:27:11]

Nit: Refactor this into a local bool and use that var in the macro.

[Thiemo Nagel, 2014/05/26 17:54:30]

Done.

+  }
+
   switch (device_settings_service_->status()) {
     case chromeos::DeviceSettingsService::STORE_SUCCESS: {
       status_ = STATUS_OK;