Introduce AudioSourceProviderClientLockScope.

It makes lock/unlock of AudioSourceProviderClient easier.
This class holds a strong reference to AudioSourceProviderClient. So we
don't need MediaElementAudioSourceNode::m_keepAliveWhileLocking.

BUG=395940

Review URL: https://codereview.chromium.org/416333002

git-svn-id: svn://svn.chromium.org/blink/trunk@178999 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/html/HTMLMediaElement.cpp

@@ -168,6 +168,30 @@ private:
     RawPtrWillBeMember<HTMLMediaElement> m_mediaElement;
 };
 
+class AudioSourceProviderClientLockScope {
+    STACK_ALLOCATED();
+public:
+#if ENABLE(WEB_AUDIO)
+    AudioSourceProviderClientLockScope(HTMLMediaElement& element)
+        : m_client(element.audioSourceNode())
+    {
+        if (m_client)
+            m_client->lock();
+    }
+    ~AudioSourceProviderClientLockScope()
+    {
+        if (m_client)
+            m_client->unlock();
+    }
+
+private:
+    RawPtrWillBeMember<AudioSourceProviderClient> m_client;
+#else
+    explicit AudioSourceProviderClientLockScope(HTMLMediaElement&) { }
+    ~AudioSourceProviderClientLockScope() { }
+#endif
+};
+
 static const AtomicString& AudioKindToString(WebMediaPlayerClient::AudioTrackKind kind)
 {
     switch (kind) {
@@ -3393,17 +3417,10 @@ void HTMLMediaElement::clearMediaPlayer(int flags)
 
     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();
@@ -3688,22 +3705,16 @@ void* HTMLMediaElement::preDispatchEventHandler(Event* event)
 
 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
 }
@@ -3713,14 +3724,9 @@ 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()

third_party/WebKit/Source/modules/webaudio/MediaElementAudioSourceNode.cpp

@@ -147,14 +147,18 @@ void MediaElementAudioSourceNode::process(size_t numberOfFrames)
 
 void MediaElementAudioSourceNode::lock()
 {
-    m_keepAliveWhileLocking = this;
+#if !ENABLE(OILPAN)
+    ref();
+#endif
     m_processLock.lock();
 }
 
 void MediaElementAudioSourceNode::unlock()
 {
     m_processLock.unlock();
-    m_keepAliveWhileLocking.clear();
+#if !ENABLE(OILPAN)
+    deref();
+#endif
 }
 
 void MediaElementAudioSourceNode::trace(Visitor* visitor)

third_party/WebKit/Source/modules/webaudio/MediaElementAudioSourceNode.h

@@ -73,9 +73,6 @@ private:
     double m_sourceSampleRate;
 
     OwnPtr<MultiChannelResampler> m_multiChannelResampler;
-    // Oilpan: This object must be alive between lock() and unlock().
-    GC_PLUGIN_IGNORE("http://crbug.com/395940")
-    RefPtrWillBePersistent<MediaElementAudioSourceNode> m_keepAliveWhileLocking;
 };
 
 } // namespace blink

third_party/WebKit/Source/platform/audio/AudioSourceProviderClient.h

@@ -32,6 +32,7 @@ namespace blink {
 class AudioSourceProviderClient : public WillBeGarbageCollectedMixin {
 public:
     virtual void setFormat(size_t numberOfChannels, float sampleRate) = 0;
+    // Oilpan: Callers should keep this object alive during lock() and unlock().
     virtual void lock() { }
     virtual void unlock() { }
     virtual void trace(Visitor*) { }