Add fake for InstanceIDWithSubtype.java, in order to re-use unit test

components/gcm_driver/instance_id/instance_id_android.h

Index: components/gcm_driver/instance_id/instance_id_android.h
diff --git a/components/gcm_driver/instance_id/instance_id_android.h b/components/gcm_driver/instance_id/instance_id_android.h
index a11529604142cc774d0a96cf0e208ef3e6386a97..f27a4867d48493af9f5ba74d5533e93f0255d9b1 100644
--- a/components/gcm_driver/instance_id/instance_id_android.h
+++ b/components/gcm_driver/instance_id/instance_id_android.h
@@ -27,6 +27,11 @@ class InstanceIDAndroid : public InstanceID {
   // Register JNI methods.
   static bool RegisterJni(JNIEnv* env);
 
+  // Tests depending on InstanceID that run without a nested Java message loop
+  // must enable this. Operations that would normally be asynchronous will
+  // instead block the UI thread. Reset it to false when tearing down.
+  static void SetBlockOnAsyncTasksForTesting(bool block);
+
   InstanceIDAndroid(const std::string& app_id);
   ~InstanceIDAndroid() override;