Another fix for MediaSessionAndroid DCHECK on destruction

content/browser/media/session/media_session_android.cc

 // Copyright 2016 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 "content/browser/media/session/media_session_android.h"
 
 #include <algorithm>
 #include "content/browser/media/session/media_session_impl.h"
 #include "content/browser/web_contents/web_contents_android.h"
 #include "content/browser/web_contents/web_contents_impl.h"
@@ skipping 18 matching lines @@
   JNIEnv* env = base::android::AttachCurrentThread();
   ScopedJavaLocalRef<jobject> j_media_session =
       Java_MediaSessionImpl_create(env, reinterpret_cast<intptr_t>(this));
   j_media_session_ = JavaObjectWeakGlobalRef(env, j_media_session);
 
   WebContentsAndroid* contents_android = GetWebContentsAndroid();
   if (contents_android)
     contents_android->SetMediaSession(j_media_session);
 }
 
-MediaSessionAndroid::~MediaSessionAndroid() {
-  // MediaSessionDestroyed() should have already been called.
-  DCHECK(j_media_session_.is_empty());
-}
+MediaSessionAndroid::~MediaSessionAndroid() = default;
 
 // static
 bool MediaSessionAndroid::Register(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
 
 // static
 ScopedJavaLocalRef<jobject> GetMediaSessionFromWebContents(
     JNIEnv* env,
     const JavaParamRef<jclass>& clazz,
     const JavaParamRef<jobject>& j_contents_android) {
   WebContents* contents = WebContents::FromJavaWebContents(j_contents_android);
   if (!contents)
     return ScopedJavaLocalRef<jobject>();
 
   MediaSessionImpl* session = MediaSessionImpl::Get(contents);
   DCHECK(session);
   return MediaSessionAndroid::JavaObjectGetter::GetJavaObject(
       session->session_android());
 }
 
 void MediaSessionAndroid::MediaSessionDestroyed() {
   ScopedJavaLocalRef<jobject> j_local_session = GetJavaObject();
   if (j_local_session.is_null()) {
     // If the Java MediaSession is already garbage collected, unset the weak
     // Java reference.
     j_media_session_.reset();

[boliu, 2016/11/04 00:42:00]

you can drop this as well then

[Zhiqiang Zhang (Slow), 2016/11/04 00:47:56]

Done.

     return;
   }
 
   JNIEnv* env = base::android::AttachCurrentThread();
   // The Java object will tear down after this call.
   Java_MediaSessionImpl_mediaSessionDestroyed(env, j_local_session);
   j_media_session_.reset();
 
   WebContentsAndroid* contents_android = GetWebContentsAndroid();
   if (contents_android)
@@ skipping 90 matching lines @@
     return nullptr;
   return contents->GetWebContentsAndroid();
 }
 
 ScopedJavaLocalRef<jobject> MediaSessionAndroid::GetJavaObject() {
   JNIEnv* env = base::android::AttachCurrentThread();
   return j_media_session_.get(env);
 }
 
 }  // namespace content