Implementation of 'AudioContext.getOutputTimestamp' method

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

Index: third_party/WebKit/Source/modules/webaudio/BaseAudioContext.cpp
diff --git a/third_party/WebKit/Source/modules/webaudio/BaseAudioContext.cpp b/third_party/WebKit/Source/modules/webaudio/BaseAudioContext.cpp
index 020e539047db244fcc9878bc8f9e5da1fe0beefa..e70e02f261dc63f3c917cab8641dbe81bbc3af15 100644
--- a/third_party/WebKit/Source/modules/webaudio/BaseAudioContext.cpp
+++ b/third_party/WebKit/Source/modules/webaudio/BaseAudioContext.cpp
@@ -102,7 +102,8 @@ BaseAudioContext::BaseAudioContext(Document* document)
       m_periodicWaveSine(nullptr),
       m_periodicWaveSquare(nullptr),
       m_periodicWaveSawtooth(nullptr),
-      m_periodicWaveTriangle(nullptr) {
+      m_periodicWaveTriangle(nullptr),
+      m_outputPosition() {

[Raymond Toy, 2016/11/04 17:51:40]

Don't you want to initialize this to something?  It's possible for the context
to be suspended at startup so if it gets queried, the output position will be
random junk.

[Mikhail, 2016/11/07 18:28:03]

this invokes "default" constructor for the structure, so both position and
timestamp are set to zero.

   // If mediaPlaybackRequiresUserGesture is enabled, cross origin iframes will
   // require user gesture for the AudioContext to produce sound.
   if (document->settings() &&
@@ -135,7 +136,8 @@ BaseAudioContext::BaseAudioContext(Document* document,
       m_periodicWaveSine(nullptr),
       m_periodicWaveSquare(nullptr),
       m_periodicWaveSawtooth(nullptr),
-      m_periodicWaveTriangle(nullptr) {}
+      m_periodicWaveTriangle(nullptr),
+      m_outputPosition() {}
 
 BaseAudioContext::~BaseAudioContext() {
   deferredTaskHandler().contextWillBeDestroyed();
@@ -706,7 +708,8 @@ void BaseAudioContext::handleStoppableSourceNodes() {
   }
 }
 
-void BaseAudioContext::handlePreRenderTasks() {
+void BaseAudioContext::handlePreRenderTasks(
+    const AudioIOPosition& outputPosition) {
   DCHECK(isAudioThread());
 
   // At the beginning of every render quantum, try to update the internal
@@ -724,6 +727,9 @@ void BaseAudioContext::handlePreRenderTasks() {
     // Update the dirty state of the listener.
     listener()->updateState();
 
+    // Update output timestamp.
+    m_outputPosition = outputPosition;
+
     unlock();
   }
 }
@@ -817,6 +823,11 @@ bool BaseAudioContext::isAllowedToStart() const {
   return false;
 }
 
+AudioIOPosition BaseAudioContext::outputPosition() {
+  AutoLocker locker(this);
+  return m_outputPosition;
+}
+
 void BaseAudioContext::rejectPendingResolvers() {
   DCHECK(isMainThread());