Integrate InstanceID with GCM crypto provider

components/gcm_driver/instance_id/instance_id_driver_unittest.cc

Index: components/gcm_driver/instance_id/instance_id_driver_unittest.cc
diff --git a/components/gcm_driver/instance_id/instance_id_driver_unittest.cc b/components/gcm_driver/instance_id/instance_id_driver_unittest.cc
index e34f5773d24d2464946c13cc0d57d0a1d0206944..7b4e722e01c9021fa2de916592c4e6e98abc86a9 100644
--- a/components/gcm_driver/instance_id/instance_id_driver_unittest.cc
+++ b/components/gcm_driver/instance_id/instance_id_driver_unittest.cc
@@ -120,7 +120,13 @@ void InstanceIDDriverTest::SetUp() {
   RecreateInstanceIDDriver();
 }
 
-void InstanceIDDriverTest::TearDown() {}
+void InstanceIDDriverTest::TearDown() {
+  driver_.reset();
+  gcm_driver_.reset();
+  // |gcm_driver_| owns a GCMKeyStore that owns a ProtoDatabaseImpl whose
+  // destructor deletes the underlying LevelDB on the task runner.
+  base::RunLoop().RunUntilIdle();
+}
 
 void InstanceIDDriverTest::RecreateInstanceIDDriver() {
   driver_.reset(new InstanceIDDriver(gcm_driver_.get()));