Implement BluetoothRemoteGattCharacteristicWin::StartNotifySession and related unit tests

device/bluetooth/test/bluetooth_test.h

Index: device/bluetooth/test/bluetooth_test.h
diff --git a/device/bluetooth/test/bluetooth_test.h b/device/bluetooth/test/bluetooth_test.h
index 5570ca11f1f7ffd0a6b23ea624d27fcfe28b3f39..95f33accbd5a18f719ff11fa3e22e39991e42939 100644
--- a/device/bluetooth/test/bluetooth_test.h
+++ b/device/bluetooth/test/bluetooth_test.h
@@ -197,6 +197,9 @@ class BluetoothTestBase : public testing::Test {
   // Removes the device from the adapter and deletes it.
   virtual void DeleteDevice(BluetoothDevice* device);
 
+  // Run all pending tasks until idle.
+  virtual void RunUntilIdle();
+
   // Callbacks that increment |callback_count_|, |error_callback_count_|:
   void Callback(Call expected);
   void DiscoverySessionCallback(Call expected,