Report Bluetooth adapter status to UMA.

chrome/browser/signin/easy_unlock_service.cc

Index: chrome/browser/signin/easy_unlock_service.cc
diff --git a/chrome/browser/signin/easy_unlock_service.cc b/chrome/browser/signin/easy_unlock_service.cc
index 7cfe4523f0a4e34f94a5c673e667e67f7bd7728e..da4b694d47d1d91c0468b87c83c0d0ccb3d9d258 100644
--- a/chrome/browser/signin/easy_unlock_service.cc
+++ b/chrome/browser/signin/easy_unlock_service.cc
@@ -44,8 +44,19 @@
 #include "components/user_manager/user_manager.h"
 #endif
 
+#if defined(OS_WIN)
+#include "base/win/windows_version.h"
+#endif
+
 namespace {
 
+enum BluetoothType {
+  BT_NO_ADAPTER,
+  BT_NORMAL,
+  BT_LOW_ENERGY_CAPABLE,
+  BT_MAX_TYPE
+};
+
 PrefService* GetLocalState() {
   return g_browser_process ? g_browser_process->local_state() : NULL;
 }
@@ -118,6 +129,10 @@ class EasyUnlockService::BluetoothDetector
     service_->OnBluetoothAdapterPresentChanged();
   }
 
+  device::BluetoothAdapter* getAdapter() {
+    return adapter_.get();
+  }
+
  private:
   void OnAdapterInitialized(scoped_refptr<device::BluetoothAdapter> adapter) {
     adapter_ = adapter;
@@ -129,6 +144,17 @@ class EasyUnlockService::BluetoothDetector
     // toes in the future then we need to revisit this guard.
     if (adapter_->IsDiscoverable())
       TurnOffBluetoothDiscoverability();
+
+#if !defined(OS_CHROMEOS)
+    // Bluetooth detection causes serious performance degradations on Mac
+    // and possibly other platforms as well: http://crbug.com/467316
+    // Since this feature is currently only offered for ChromeOS we just
+    // turn it off on other platforms once the inforamtion about the
+    // adapter has been gathered and reported.
+    // TODO(bcwhite,xiyuan): Revisit when non-chromeos platforms are supported.
+    adapter_->RemoveObserver(this);
+    adapter_ = NULL;
+#endif  // !defined(OS_CHROMEOS)
   }
 
   // apps::AppLifetimeMonitor::Observer:
@@ -664,20 +690,31 @@ void EasyUnlockService::InitializeOnAppManagerReady() {
   CHECK(app_manager_.get());
 
   InitializeInternal();
-
-#if defined(OS_CHROMEOS)
-  // Only start Bluetooth detection for ChromeOS since the feature is
-  // only offered on ChromeOS. Enabling this on non-ChromeOS platforms
-  // previously introduced a performance regression: http://crbug.com/404482
-  // Make sure not to reintroduce a performance regression if re-enabling on
-  // additional platforms.
-  // TODO(xiyuan): Revisit when non-chromeos platforms are supported.
   bluetooth_detector_->Initialize();
-#endif  // defined(OS_CHROMEOS)
 }
 
 void EasyUnlockService::OnBluetoothAdapterPresentChanged() {
   UpdateAppState();
+
+  // Whether we've already passed Bluetooth availability information to UMA.
+  // This is static because there may be multiple instances and we want to
+  // report this system-level stat only once per run of Chrome.
+  static bool bluetooth_adapter_has_been_reported = false;
+
+  if (!bluetooth_adapter_has_been_reported) {
+    bluetooth_adapter_has_been_reported = true;
+    int bttype = BT_NO_ADAPTER;
+    if (bluetooth_detector_->IsPresent()) {
+      bttype = BT_LOW_ENERGY_CAPABLE;
+#if defined(OS_WIN)
+      if (base::win::GetVersion() < base::win::VERSION_WIN8) {
+        bttype = BT_NORMAL;
+      }
+#endif
+    }
+    UMA_HISTOGRAM_ENUMERATION(
+      "EasyUnlock.BluetoothAvailability", bttype, BT_MAX_TYPE);
+  }
 }
 
 void EasyUnlockService::SetHardlockStateForUser(