Add UMA histograms for WebAudio

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

Index: third_party/WebKit/Source/modules/webaudio/AudioContext.cpp
diff --git a/third_party/WebKit/Source/modules/webaudio/AudioContext.cpp b/third_party/WebKit/Source/modules/webaudio/AudioContext.cpp
index ecaffd59494a65c28508c31ca42b1d9fabb61eda..f7cc9c928a7f3b814c40749e345b535337eaaf75 100644
--- a/third_party/WebKit/Source/modules/webaudio/AudioContext.cpp
+++ b/third_party/WebKit/Source/modules/webaudio/AudioContext.cpp
@@ -10,6 +10,7 @@
 #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
@@ -66,6 +67,13 @@ AbstractAudioContext* AudioContext::create(Document& document, ExceptionState& e
         audioContext, audioContext->m_contextId, s_hardwareContextCount);
 #endif
 
+    DEFINE_STATIC_LOCAL(SparseHistogram, maxChannelCountHistogram,
+        ("WebAudio.AudioContext.MaxChannelsAvailable"));
+    DEFINE_STATIC_LOCAL(SparseHistogram, sampleRateHistogram,
+        ("WebAudio.AudioContext.HardwareSampleRate"));
+    maxChannelCountHistogram.sample(audioContext->destination()->maxChannelCount());
+    sampleRateHistogram.sample(audioContext->sampleRate());
+
     return audioContext;
 }