Bug 1069868 - Set Bluetooth property |discoverable| to |false| after Bluetooth enabled. r=shuang

Bluetooth scan mode is BT_SCAN_MODE_CONNECTABLE by default, it means it
should be connectable and non-discoverable.

dom/bluetooth/bluedroid/BluetoothServiceBluedroid.cpp

@@ -92,10 +92,11 @@ public:
     sSetPropertyRunnableArray.Clear();
     sUnbondingRunnableArray.Clear();
 
-    // Bluetooth scan mode is NONE by default
+    // Bluetooth scan mode is SCAN_MODE_CONNECTABLE by default, i.e., It should
+    // be connectable and non-discoverable.
     NS_ENSURE_TRUE(sBtInterface, NS_ERROR_FAILURE);
     sBtInterface->SetAdapterProperty(
-      BluetoothNamedValue(NS_ConvertUTF8toUTF16("Discoverable"), true),
+      BluetoothNamedValue(NS_ConvertUTF8toUTF16("Discoverable"), false),
       new SetAdapterPropertyResultHandler());
 
     // Try to fire event 'AdapterAdded' to fit the original behaviour when

dom/bluetooth2/bluedroid/BluetoothServiceBluedroid.cpp

@@ -107,10 +107,11 @@ public:
     sBondingRunnableArray.Clear();
     sUnbondingRunnableArray.Clear();
 
-    // Bluetooth scan mode is NONE by default
+    // Bluetooth scan mode is SCAN_MODE_CONNECTABLE by default, i.e., It should
+    // be connectable and non-discoverable.
     NS_ENSURE_TRUE(sBtInterface, NS_ERROR_FAILURE);
     sBtInterface->SetAdapterProperty(
-      BluetoothNamedValue(NS_ConvertUTF8toUTF16("Discoverable"), true),
+      BluetoothNamedValue(NS_ConvertUTF8toUTF16("Discoverable"), false),
       new SetAdapterPropertyResultHandler());
 
     // Trigger BluetoothOppManager to listen