Add UMA histograms for WebAudio

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

Index: third_party/WebKit/Source/modules/webaudio/OfflineAudioContext.cpp
diff --git a/third_party/WebKit/Source/modules/webaudio/OfflineAudioContext.cpp b/third_party/WebKit/Source/modules/webaudio/OfflineAudioContext.cpp
index dc3afb966c3be24c02b0a5c034ddb0727f8a75d7..3edf3d77f2cfdd1270762b6d05180ddb6f60c6b8 100644
--- a/third_party/WebKit/Source/modules/webaudio/OfflineAudioContext.cpp
+++ b/third_party/WebKit/Source/modules/webaudio/OfflineAudioContext.cpp
@@ -35,6 +35,7 @@
 #include "modules/webaudio/OfflineAudioCompletionEvent.h"
 #include "modules/webaudio/OfflineAudioDestinationNode.h"
 
+#include "platform/Histogram.h"
 #include "platform/audio/AudioUtilities.h"
 
 namespace blink {
@@ -90,6 +91,17 @@ OfflineAudioContext* OfflineAudioContext::create(ExecutionContext* context, unsi
             + ")");
     }
 
+    DEFINE_STATIC_LOCAL(SparseHistogram, offlineContextChannelCountHistogram,
+        ("WebAudio.OfflineAudioContext.ChannelCount"));
+    DEFINE_STATIC_LOCAL(SparseHistogram, offlineContextSampleRateHistogram,
+        ("WebAudio.OfflineAudioContext.SampleRate"));
+    DEFINE_STATIC_LOCAL(SparseHistogram, offlineContextLengthHistogram,
+        ("WebAudio.OfflineAudioContext.Length"));
+
+    offlineContextChannelCountHistogram.sample(numberOfChannels);
+    offlineContextSampleRateHistogram.sample(static_cast<int>(sampleRate));
+    offlineContextLengthHistogram.sample(clampTo(numberOfFrames, 0, std::numeric_limits<int>::max()));
+
     audioContext->suspendIfNeeded();
     return audioContext;
 }