jni_helpers: Optimize IsNull()

webrtc/api/java/jni/jni_helpers.cc

 /*
  *  Copyright 2015 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 #include "webrtc/api/java/jni/jni_helpers.h"
@@ skipping 184 matching lines @@
   CHECK_EXCEPTION(jni) << "error during GetIntField";
   return i;
 }
 
 bool GetBooleanField(JNIEnv* jni, jobject object, jfieldID id) {
   jboolean b = jni->GetBooleanField(object, id);
   CHECK_EXCEPTION(jni) << "error during GetBooleanField";
   return b;
 }
 
-// Java references to "null" can only be distinguished as such in C++ by
-// creating a local reference, so this helper wraps that logic.
 bool IsNull(JNIEnv* jni, jobject obj) {
-  ScopedLocalRefFrame local_ref_frame(jni);
-  return jni->NewLocalRef(obj) == NULL;
+  return jni->IsSameObject(obj, nullptr);
 }
 
 // Given a UTF-8 encoded |native| string return a new (UTF-16) jstring.
 jstring JavaStringFromStdString(JNIEnv* jni, const std::string& native) {
   jstring jstr = jni->NewStringUTF(native.c_str());
   CHECK_EXCEPTION(jni) << "error during NewStringUTF";
   return jstr;
 }
 
 // Given a (UTF-16) jstring return a new UTF-8 native string.
@@ skipping 49 matching lines @@
 // callbacks (i.e. entry points that don't originate in a Java callstack
 // through a "native" method call).
 ScopedLocalRefFrame::ScopedLocalRefFrame(JNIEnv* jni) : jni_(jni) {
   RTC_CHECK(!jni_->PushLocalFrame(0)) << "Failed to PushLocalFrame";
 }
 ScopedLocalRefFrame::~ScopedLocalRefFrame() {
   jni_->PopLocalFrame(NULL);
 }
 
 }  // namespace webrtc_jni