Add UMA histograms for WebAudio

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "modules/webaudio/AudioContext.h"
 
 #include "bindings/core/v8/ExceptionMessages.h"
 #include "bindings/core/v8/ExceptionState.h"
 #include "bindings/core/v8/ScriptPromiseResolver.h"
 #include "core/dom/DOMException.h"
 #include "core/dom/ExceptionCode.h"
 #include "modules/webaudio/AudioBufferCallback.h"
+#include "platform/Histogram.h"
 #include "platform/audio/AudioUtilities.h"
 
 #if DEBUG_AUDIONODE_REFERENCES
 #include <stdio.h>
 #endif
 
 namespace blink {
 
 // Don't allow more than this number of simultaneous AudioContexts
 // talking to hardware.
@@ skipping 36 matching lines @@
     // quantum". NOTE: for now AudioContext does not need an explicit
     // startRendering() call from JavaScript.  We may want to consider
     // requiring it for symmetry with OfflineAudioContext.
     audioContext->startRendering();
     ++s_hardwareContextCount;
 #if DEBUG_AUDIONODE_REFERENCES
     fprintf(stderr, "%p: AudioContext::AudioContext(): %u #%u\n",
         audioContext, audioContext->m_contextId, s_hardwareContextCount);
 #endif
 
+    DEFINE_STATIC_LOCAL(SparseHistogram, maxChannelCountHistogram,
+        ("WebAudio.AudioContext.MaxChannelsAvailable"));
+    DEFINE_STATIC_LOCAL(SparseHistogram, sampleRateHistogram,
+        ("WebAudio.AudioContext.HardwareSampleRate"));

[Mark P, 2016/06/10 04:02:53]

Is this generally fixed or should this be a custom histogram too?

[Raymond Toy, 2016/06/10 15:13:44]

We expect the possible values for the hardware sample rate to be from a fairly
small set.  Our expectations are that 44100, 48000, 88200, 96000, and 192000
represent basically all of the possible values.  We have some suspicions that
there are some other values, though and we'd like to capture the actual value.

+    maxChannelCountHistogram.sample(audioContext->destination()->maxChannelCount());
+    sampleRateHistogram.sample(audioContext->sampleRate());
+
     return audioContext;
 }
 
 AudioContext::AudioContext(Document& document)
     : AbstractAudioContext(&document)
     , m_contextId(s_contextId++)
 {
 }
 
 AudioContext::~AudioContext()
@@ skipping 114 matching lines @@
     ASSERT(destination());
 
     if (contextState() == Running) {
         destination()->audioDestinationHandler().stopRendering();
         setContextState(Suspended);
         deferredTaskHandler().clearHandlersToBeDeleted();
     }
 }
 
 } // namespace blink