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

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

Index: third_party/WebKit/Source/modules/webaudio/BaseAudioContext.h
diff --git a/third_party/WebKit/Source/modules/webaudio/BaseAudioContext.h b/third_party/WebKit/Source/modules/webaudio/BaseAudioContext.h
index aa2c5f8b54237da92aaa41b11396e1e9d9880e97..b20366804aef02c442a5a4625ae6f4f916b4d417 100644
--- a/third_party/WebKit/Source/modules/webaudio/BaseAudioContext.h
+++ b/third_party/WebKit/Source/modules/webaudio/BaseAudioContext.h
@@ -54,6 +54,7 @@ class AudioBufferCallback;
 class AudioBufferSourceNode;
 class AudioListener;
 class AudioSummingJunction;
+class BaseAudioContextTest;
 class BiquadFilterNode;
 class ChannelMergerNode;
 class ChannelSplitterNode;
@@ -297,6 +298,11 @@ class MODULES_EXPORT BaseAudioContext : public EventTargetWithInlineData,
   // 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*,
@@ -340,6 +346,18 @@ class MODULES_EXPORT BaseAudioContext : public EventTargetWithInlineData,
   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();
 
@@ -381,6 +399,9 @@ class MODULES_EXPORT BaseAudioContext : public EventTargetWithInlineData,
   // 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.
@@ -420,6 +441,8 @@ class MODULES_EXPORT BaseAudioContext : public EventTargetWithInlineData,
   // 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