ash: Add a bluetooth entry in the uber tray.

ash/system/tray/system_tray.cc

Index: ash/system/tray/system_tray.cc
diff --git a/ash/system/tray/system_tray.cc b/ash/system/tray/system_tray.cc
index b116b1f659a5e88ba70839b47064781d7a3b8d13..ac9ca7652dff24f2fe396466f1d34a9bf072e127 100644
--- a/ash/system/tray/system_tray.cc
+++ b/ash/system/tray/system_tray.cc
@@ -376,10 +376,18 @@ NetworkIconInfo::NetworkIconInfo()
 NetworkIconInfo::~NetworkIconInfo() {
 }
 
+BluetoothDeviceInfo::BluetoothDeviceInfo()
+    : connected(false) {
+}
+
+BluetoothDeviceInfo::~BluetoothDeviceInfo() {
+}
+
 SystemTray::SystemTray()
     : items_(),
       accessibility_observer_(NULL),
       audio_observer_(NULL),
+      bluetooth_observer_(NULL),
       brightness_observer_(NULL),
       caps_lock_observer_(NULL),
       clock_observer_(NULL),