Add UMA histograms for WebAudio

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

 /*
  * 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 46 matching lines @@
 #include "modules/webaudio/OfflineAudioCompletionEvent.h"
 #include "modules/webaudio/OfflineAudioContext.h"
 #include "modules/webaudio/OfflineAudioDestinationNode.h"
 #include "modules/webaudio/OscillatorNode.h"
 #include "modules/webaudio/PannerNode.h"
 #include "modules/webaudio/PeriodicWave.h"
 #include "modules/webaudio/PeriodicWaveConstraints.h"
 #include "modules/webaudio/ScriptProcessorNode.h"
 #include "modules/webaudio/StereoPannerNode.h"
 #include "modules/webaudio/WaveShaperNode.h"
+#include "platform/Histogram.h"
 #include "platform/ThreadSafeFunctional.h"
 #include "platform/audio/IIRFilter.h"
 #include "public/platform/Platform.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 
 AbstractAudioContext* AbstractAudioContext::create(Document& document, ExceptionState& exceptionState)
 {
     return AudioContext::create(document, exceptionState);
@@ skipping 122 matching lines @@
 void AbstractAudioContext::throwExceptionForClosedState(ExceptionState& exceptionState)
 {
     exceptionState.throwDOMException(InvalidStateError, "AudioContext has been closed.");
 }
 
 AudioBuffer* AbstractAudioContext::createBuffer(unsigned numberOfChannels, size_t numberOfFrames, float sampleRate, ExceptionState& exceptionState)
 {
     // It's ok to call createBuffer, even if the context is closed because the AudioBuffer doesn't
     // really "belong" to any particular context.
 
-    return AudioBuffer::create(numberOfChannels, numberOfFrames, sampleRate, exceptionState);
+    AudioBuffer* buffer = AudioBuffer::create(numberOfChannels, numberOfFrames, sampleRate, exceptionState);
+
+    if (buffer) {
+        // Only record the data if the creation succeeded.
+        DEFINE_STATIC_LOCAL(SparseHistogram, audioBufferChannelsHistogram,
+            ("WebAudio.AudioBuffer.NumberOfChannels"));
+        DEFINE_STATIC_LOCAL(SparseHistogram, audioBufferLengthHistogram,
+            ("WebAudio.AudioBuffer.Length"));
+        DEFINE_STATIC_LOCAL(SparseHistogram, audioBufferSampleRateHistogram,

[hongchan, 2016/05/18 22:07:01]

I think we can move anything related to the sample rate to the inside of if()
clause below.

[Raymond Toy, 2016/05/18 22:25:30]

The sample rate for the buffer is an argument to createBuffer.  So you only want
to record the sample rate only for contexts that aren't closed?  I think we
would get more (indirect) information if we always record the sample rate but
only record the ratio when the context is not closed.  Then the difference
between the number of samples taken between the two tells us how often people
create buffers on closed contexts. 

But sample rate ratio histogram can, of course, go inside the if block below.

[hongchan, 2016/05/19 21:43:53]

Acknowledged.

+            ("WebAudio.AudioBuffer.SampleRate"));
+        DEFINE_STATIC_LOCAL(SparseHistogram, audioBufferSampleRateRatioHistogram,

[hongchan, 2016/05/19 21:43:53]

Yes, I think this needs to be inside of the if clause below.

[Raymond Toy, 2016/05/20 20:21:25]

Done.

+            ("WebAudio.AudioBuffer.SampleRateRatio"));
+        audioBufferChannelsHistogram.sample(numberOfChannels);
+        audioBufferLengthHistogram.sample(clampTo(numberOfFrames, 0, std::numeric_limits<int>::max()));
+        audioBufferSampleRateHistogram.sample(static_cast<int>(sampleRate));
+
+        // Compute the ratio of the buffer rate and the context rate so we know
+        // how often the buffer needs to be resampled to match the context.  For
+        // the histogram, we multiply the ratio by 100 and round to the nearest
+        // integer.  If the context is closed, don't record this because we
+        // don't have a sample rate for closed context.
+        if (!isContextClosed()) {
+            float ratio = 100 * sampleRate / this->sampleRate();
+            audioBufferSampleRateRatioHistogram.sample(static_cast<int>(ratio + 0.5));
+        }
+    }
+
+    return buffer;
 }
 
 ScriptPromise AbstractAudioContext::decodeAudioData(ScriptState* scriptState, DOMArrayBuffer* audioData, AudioBufferCallback* successCallback, AudioBufferCallback* errorCallback, ExceptionState& exceptionState)
 {
     ASSERT(isMainThread());
     ASSERT(audioData);
 
     ScriptPromiseResolver* resolver = ScriptPromiseResolver::create(scriptState);
     ScriptPromise promise = resolver->promise();
 
@@ skipping 761 matching lines @@
 
 SecurityOrigin* AbstractAudioContext::getSecurityOrigin() const
 {
     if (getExecutionContext())
         return getExecutionContext()->getSecurityOrigin();
 
     return nullptr;
 }
 
 } // namespace blink