Add missing using statements for JNI types.

base/android/memory_pressure_listener_android.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/android/memory_pressure_listener_android.h"
 
 #include "base/android/context_utils.h"
 #include "base/memory/memory_pressure_listener.h"
 #include "jni/MemoryPressureListener_jni.h"
 
+using base::android::JavaParamRef;
+
 // Defined and called by JNI.
 static void OnMemoryPressure(JNIEnv* env,
                              const JavaParamRef<jclass>& clazz,
                              jint memory_pressure_level) {
   base::MemoryPressureListener::NotifyMemoryPressure(
       static_cast<base::MemoryPressureListener::MemoryPressureLevel>(
           memory_pressure_level));
 }
 
 namespace base {
 namespace android {
 
 bool MemoryPressureListenerAndroid::Register(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
 
 void MemoryPressureListenerAndroid::RegisterSystemCallback(JNIEnv* env) {
   Java_MemoryPressureListener_registerSystemCallback(
       env, GetApplicationContext());
 }
 
 }  // namespace android
 }  // namespace base