Web Audio: record autoplay status when an AudioContext is destroyed.

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

 /*
  * Copyright (C) 2010, Google 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 36 matching lines @@
 #include "wtf/build_config.h"
 
 namespace blink {
 
 class AnalyserNode;
 class AudioBuffer;
 class AudioBufferCallback;
 class AudioBufferSourceNode;
 class AudioListener;
 class AudioSummingJunction;
+class BaseAudioContextTest;
 class BiquadFilterNode;
 class ChannelMergerNode;
 class ChannelSplitterNode;
 class ConvolverNode;
 class DelayNode;
 class Dictionary;
 class Document;
 class DynamicsCompressorNode;
 class ExceptionState;
 class GainNode;
@@ skipping 223 matching lines @@
   //  - it has been stopped by its execution context.
   virtual bool isContextClosed() const { return m_isCleared; }
 
   // Get the security origin for this audio context.
   SecurityOrigin* getSecurityOrigin() const;
 
   // Get the PeriodicWave for the specified oscillator type.  The table is
   // initialized internally if necessary.
   PeriodicWave* periodicWave(int type);
 
+  // For metrics purpose, records when start() is called on a
+  // AudioScheduledSourceHandler or a AudioBufferSourceHandler without a user
+  // gesture while the AudioContext is locked.
+  void maybeRecordStartAttempt();
+
  protected:
   explicit BaseAudioContext(Document*);
   BaseAudioContext(Document*,
                    unsigned numberOfChannels,
                    size_t numberOfFrames,
                    float sampleRate);
 
   void initialize();
   void uninitialize();
 
@@ skipping 23 matching lines @@
   void rejectPendingDecodeAudioDataResolvers();
 
   // If any, unlock user gesture requirements if a user gesture is being
   // processed.
   void maybeUnlockUserGesture();
 
   // Returns whether the AudioContext is allowed to start rendering.
   bool isAllowedToStart() const;
 
  private:
+  friend class BaseAudioContextTest;
+
+  // Do not change the order of this enum, it is used for metrics.
+  enum AutoplayStatus {

[Raymond Toy, 2016/10/10 17:05:10]

"AutoPlay" or "Autoplay"? If you had written complete words, it would be
"AutoPlay", I think.

[mlamouri (slow - plz ping), 2016/10/10 18:44:40]

We use "autoplay" in one word in Chrome (and most products nowadays)

+    AutoplayStatusFailed = 0,

[Raymond Toy, 2016/10/10 17:05:10]

This doesn't seem to quite match the histogram enum description.  What does this
really mean? Maybe add comments on what this really means?

[mlamouri (slow - plz ping), 2016/10/10 18:44:40]

Sorry about this, I forgot to update the histograms.xml file.

+    AutoplayStatusFailedWithStart = 1,
+    AutoplayStatusSucceeded = 3,

[Raymond Toy, 2016/10/10 17:05:10]

Why 3 and not 2?

Plus, this doesn't match the histogram values, which includes 2.

[mlamouri (slow - plz ping), 2016/10/10 18:44:40]

Oups. Same cause, I changed histograms and forgot to update. Sorry :-/

+
+    // Keep at the end.
+    AutoplayStatusCount
+  };
+
   bool m_isCleared;
   void clear();
 
   // When the context goes away, there might still be some sources which
   // haven't finished playing.  Make sure to release them here.
   void releaseActiveSourceNodes();
 
   void removeFinishedSourceNodes();
 
   // Listener for the PannerNodes
@@ skipping 21 matching lines @@
   // FIXME(dominicc): Move these to AudioContext because only
   // it creates these Promises.
   // Handle Promises for resume() and suspend()
   void resolvePromisesForResume();
   void resolvePromisesForResumeOnMainThread();
 
   // When the context is going away, reject any pending script promise
   // resolvers.
   virtual void rejectPendingResolvers();
 
+  // Record the current autoplay status and clear it.

[Raymond Toy, 2016/10/10 17:05:10]

It seems this is intended to be called only when the context is being
destructed. If so, add a comment here with this restriction.  

Or just get rid of this function and put the body into the destructor.

+  void recordAutoplayStatus();
+
   // True if we're in the process of resolving promises for resume().  Resolving
   // can take some time and the audio context process loop is very fast, so we
   // don't want to call resolve an excessive number of times.
   bool m_isResolvingResumePromises;
 
   // Whether a user gesture is required to start this AudioContext.
   bool m_userGestureRequired;
 
   unsigned m_connectionCount;
 
@@ skipping 19 matching lines @@
   // sample rate. so they can be shared with all OscillatorNodes in the context.
   // To conserve memory, these are lazily initialized on first use.
   Member<PeriodicWave> m_periodicWaveSine;
   Member<PeriodicWave> m_periodicWaveSquare;
   Member<PeriodicWave> m_periodicWaveSawtooth;
   Member<PeriodicWave> m_periodicWaveTriangle;
 
   // This is considering 32 is large enough for multiple channels audio.
   // It is somewhat arbitrary and could be increased if necessary.
   enum { MaxNumberOfChannels = 32 };
+
+  Optional<AutoplayStatus> m_autoplayStatus;
 };
 
 }  // namespace blink
 
 #endif  // BaseAudioContext_h