Clarify AndroidStatusFetcher documentation

chrome/browser/chromeos/policy/device_status_collector.h

Index: chrome/browser/chromeos/policy/device_status_collector.h
diff --git a/chrome/browser/chromeos/policy/device_status_collector.h b/chrome/browser/chromeos/policy/device_status_collector.h
index b4988191055e9c6b47a28b6118bc64736901fb29..5d33680e92429a1db8ca2d66ae19c4a4a2c0f011 100644
--- a/chrome/browser/chromeos/policy/device_status_collector.h
+++ b/chrome/browser/chromeos/policy/device_status_collector.h
@@ -68,7 +68,10 @@ class DeviceStatusCollector {
   using AndroidStatusReceiver =
       base::Callback<void(const std::string&, const std::string&)>;
   // Calls the enterprise reporting mojo interface, passing over the
-  // AndroidStatusReceiver.
+  // AndroidStatusReceiver. Returns false if the mojo interface isn't available,
+  // in which case no asynchronous query is emitted and the android status query
+  // fails synchronously. The |AndroidStatusReceiver| is not called in this
+  // case.
   using AndroidStatusFetcher =
       base::Callback<bool(const AndroidStatusReceiver&)>;
 
@@ -79,10 +82,10 @@ class DeviceStatusCollector {
       std::unique_ptr<enterprise_management::DeviceStatusReportRequest>,
       std::unique_ptr<enterprise_management::SessionStatusReportRequest>)>;
 
-  // Constructor. Callers can inject their own VolumeInfoFetcher,
-  // CPUStatisticsFetcher and CPUTempFetcher. These callbacks are executed on
-  // Blocking Pool. A null callback can be passed for either parameter, to use
-  // the default implementation.
+  // Constructor. Callers can inject their own *Fetcher callbacks, e.g. for unit
+  // testing. A null callback can be passed for any *Fetcher parameter, to use
+  // the default implementation. These callbacks are always executed on Blocking
+  // Pool.
   DeviceStatusCollector(
       PrefService* local_state,
       chromeos::system::StatisticsProvider* provider,