Introduce AudioSourceProviderClientLockScope.

Source/core/html/HTMLMediaElement.cpp

 /*
  * Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 150 matching lines @@
     ~TrackDisplayUpdateScope()
     {
         ASSERT(m_mediaElement);
         m_mediaElement->endIgnoringTrackDisplayUpdateRequests();
     }
 
 private:
     RawPtrWillBeMember<HTMLMediaElement> m_mediaElement;
 };
 
+class AudioSourceProviderClientLockScope {
+    STACK_ALLOCATED();
+public:
+#if ENABLE(WEB_AUDIO)
+    AudioSourceProviderClientLockScope(HTMLMediaElement& element)

[haraken, 2014/07/26 04:11:37]

Add explicit.

[tkent, 2014/07/28 01:20:55]

Done.

+        : m_client(element.audioSourceNode())
+    {
+        if (m_client)
+            m_client->lock();
+    }
+    ~AudioSourceProviderClientLockScope()
+    {
+        if (m_client)
+            m_client->unlock();
+    }
+
+private:
+    RawPtrWillBeMember<AudioSourceProviderClient> m_client;

[haraken, 2014/07/26 04:11:37]

I wonder if we can just use RefPtrWillBeMember<AudioSourceProviderClient> here
and remove manual ref()/deref() in MediaElementAudioSourceNode.cpp. Since
AudioSourceProviderClientLockScope is stack-allocated, there would be no risk
for the RefPtr to produce a cycle.

[tkent, 2014/07/28 01:20:55]

Done.  But do you think Patch Set 3 is better than Patch Set 2?

+#else
+    AudioSourceProviderClientLockScope(HTMLMediaElement&) { }
+    ~AudioSourceProviderClientLockScope() { }
+#endif
+};
+
 static const AtomicString& AudioKindToString(WebMediaPlayerClient::AudioTrackKind kind)
 {
     switch (kind) {
     case WebMediaPlayerClient::AudioTrackKindNone:
         return emptyAtom;
     case WebMediaPlayerClient::AudioTrackKindAlternative:
         return AudioTrack::alternativeKeyword();
     case WebMediaPlayerClient::AudioTrackKindDescriptions:
         return AudioTrack::descriptionsKeyword();
     case WebMediaPlayerClient::AudioTrackKindMain:
@@ skipping 3205 matching lines @@
 }
 
 void HTMLMediaElement::clearMediaPlayer(int flags)
 {
     forgetResourceSpecificTracks();
 
     closeMediaSource();
 
     cancelDeferredLoad();
 
-#if ENABLE(WEB_AUDIO)
-    if (m_audioSourceNode)
-        m_audioSourceNode->lock();
-#endif
-
-    clearMediaPlayerAndAudioSourceProviderClientWithoutLocking();
-
-#if ENABLE(WEB_AUDIO)
-    if (m_audioSourceNode)
-        m_audioSourceNode->unlock();
-#endif
+    {
+        AudioSourceProviderClientLockScope scope(*this);
+        clearMediaPlayerAndAudioSourceProviderClientWithoutLocking();
+    }
 
     stopPeriodicTimers();
     m_loadTimer.stop();
 
     m_pendingActionFlags &= ~flags;
     m_loadState = WaitingForSource;
 
     if (m_textTracks)
         configureTextTrackDisplay(AssumeNoVisibleChange);
 }
@@ skipping 264 matching lines @@
 void* HTMLMediaElement::preDispatchEventHandler(Event* event)
 {
     if (event && event->type() == EventTypeNames::webkitfullscreenchange)
         configureMediaControls();
 
     return 0;
 }
 
 void HTMLMediaElement::createMediaPlayer()
 {
-#if ENABLE(WEB_AUDIO)
-    if (m_audioSourceNode)
-        m_audioSourceNode->lock();
-#endif
+    AudioSourceProviderClientLockScope scope(*this);
 
     closeMediaSource();
 
     m_player = MediaPlayer::create(this);
 
 #if ENABLE(WEB_AUDIO)
-    if (m_audioSourceNode) {
+    if (m_audioSourceNode && audioSourceProvider()) {
         // When creating the player, make sure its AudioSourceProvider knows about the client.
-        if (audioSourceProvider())
-            audioSourceProvider()->setClient(m_audioSourceNode);
-
-        m_audioSourceNode->unlock();
+        audioSourceProvider()->setClient(m_audioSourceNode);
     }
 #endif
 }
 
 #if ENABLE(WEB_AUDIO)
 void HTMLMediaElement::setAudioSourceNode(AudioSourceProviderClient* sourceNode)
 {
     m_audioSourceNode = sourceNode;
 
-    if (m_audioSourceNode)
-        m_audioSourceNode->lock();
-
+    AudioSourceProviderClientLockScope scope(*this);
     if (audioSourceProvider())
         audioSourceProvider()->setClient(m_audioSourceNode);
-
-    if (m_audioSourceNode)
-        m_audioSourceNode->unlock();
 }
 
 AudioSourceProvider* HTMLMediaElement::audioSourceProvider()
 {
     if (m_player)
         return m_player->audioSourceProvider();
 
     return 0;
 }
 #endif
@@ skipping 229 matching lines @@
 
 #if ENABLE(WEB_AUDIO)
 void HTMLMediaElement::clearWeakMembers(Visitor* visitor)
 {
     if (!visitor->isAlive(m_audioSourceNode) && audioSourceProvider())
         audioSourceProvider()->setClient(0);
 }
 #endif
 
 }