Add UMA histograms for WebAudio

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 6da7d954d04b640f9489233c8d2015acef9e054f..0c548cf106c5fd92194c03b2e4fa398b3223055f 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -60620,6 +60620,63 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="WebAudio.AudioBuffer.Length" units="frames">
+  <owner>rtoy@chromium.org</owner>
+  <owner>hongchan@chromium.org</owner>
+  <summary>
+    The length (in frames) requested by createBuffer(). Recorded for every call
+    to createBuffer(). Probably many (tens or hundreds) per page.
+  </summary>
+</histogram>
+
+<histogram name="WebAudio.AudioBuffer.NumberOfChannels">
+  <owner>rtoy@chromium.org</owner>
+  <owner>hongchan@chromium.org</owner>
+  <summary>
+    The number of channels requested by createBuffer(). Recorded for every call
+    to createBuffer(). Probably many (tens or hundreds) per page.
+  </summary>
+</histogram>
+
+<histogram name="WebAudio.AudioBuffer.SampleRate" units="Hz">
+  <owner>rtoy@chromium.org</owner>
+  <owner>hongchan@chromium.org</owner>
+  <summary>
+    The sample rate (in Hz) requested by createBuffer(). Recorded for every call
+    to createBuffer(). Probably many (tens or hundreds) per page.
+  </summary>
+</histogram>
+
+<histogram name="WebAudio.AudioBuffer.SampleRateRatio">
+  <owner>rtoy@chromium.org</owner>
+  <owner>hongchan@chromium.org</owner>
+  <summary>
+    The ratio of the buffer sample rate from createBuffer() to the context
+    sample rate. This indicates if the buffer needs to be resampled.  Recorded
+    for every call to createBuffer().  Probably many (tens or hundreds) per
+    page.
+  </summary>
+</histogram>
+
+<histogram name="WebAudio.AudioContext.HardwareSampleRate" units="Hz">
+  <owner>rtoy@chromium.org</owner>
+  <owner>hongchan@chromium.org</owner>
+  <summary>
+    The hardware sample rate (in Hz) used by an AudioContext. Recorded for every
+    WebAudio AudioContext that is created; probably only one or two per page.
+  </summary>
+</histogram>
+
+<histogram name="WebAudio.AudioContext.MaxChannelsAvailable">
+  <owner>rtoy@chromium.org</owner>
+  <owner>hongchan@chromium.org</owner>
+  <summary>
+    The maximum number of (hardware) channels available in an AudioContext.
+    Recorded for every WebAudio AudioContext that is created; probably only one
+    or two per page.
+  </summary>
+</histogram>
+
 <histogram name="WebAudio.AudioDestination.CallbackBufferSize">
   <owner>rtoy@chromium.org</owner>
   <owner>hongchan@chromium.org</owner>
@@ -60662,6 +60719,17 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="WebAudio.BiquadFilter.Type" enum="BiquadFilterType">
+  <owner>rtoy@chromium.org</owner>
+  <owner>hongchan@chromium.org</owner>
+  <summary>
+    The type of the BiquadFilterNode. Recorded each time the type is set. This
+    recorded once (to lowpass) when a biquad filter is created and also recorded
+    whenever the filter type changes due to user action or programatically. It
+    is unlikely the type will change more than once.
+  </summary>
+</histogram>
+
 <histogram name="WebAudio.IIRFilterNode.Order">
   <owner>rtoy@chromium.org</owner>
   <owner>hongchan@chromium.org</owner>
@@ -60672,6 +60740,48 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="WebAudio.OfflineAudioContext.ChannelCount">
+  <owner>rtoy@chromium.org</owner>
+  <owner>hongchan@chromium.org</owner>
+  <summary>
+    The number of channels specified for the offline audio context. Recorded for
+    every offline context created. Probably only a few per page, but could be
+    potentially much more (thousands).
+  </summary>
+</histogram>
+
+<histogram name="WebAudio.OfflineAudioContext.Length" units="frames">
+  <owner>rtoy@chromium.org</owner>
+  <owner>hongchan@chromium.org</owner>
+  <summary>
+    The length (in frames) specified for the offline audio context. Recorded for
+    every offline context created. Probably only a few per page, but could be
+    potentially much more (thousands).
+  </summary>
+</histogram>
+
+<histogram name="WebAudio.OfflineAudioContext.SampleRate" units="Hz">
+  <owner>rtoy@chromium.org</owner>
+  <owner>hongchan@chromium.org</owner>
+  <summary>
+    The sample rate (in Hz) specified for the offline audio context. Recorded
+    for every offline context created.  Probably only a few per page, but could
+    be potentially much more (thousands).
+  </summary>
+</histogram>
+
+<histogram name="WebAudio.PannerNode.PanningModel" enum="PanningModelType">
+  <owner>rtoy@chromium.org</owner>
+  <owner>hongchan@chromium.org</owner>
+  <summary>
+    The panning model for the PannerNode. Recorded once with the default value
+    at creation and once again whenver it is changed.  Once changed, it is
+    unlikely to be changed again. If there are any PannerNodes created at all,
+    then there is probably one for each source (AudioBufferSourceNode,
+    OscillatorNode, or other source).
+  </summary>
+</histogram>
+
 <histogram name="WebAudio.UserGesture" enum="UserGestureRequirement">
   <owner>mlamouri@chromium.org</owner>
   <summary>
@@ -65199,6 +65309,17 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="2" label="1+"/>
 </enum>
 
+<enum name="BiquadFilterType" type="int">
+  <int value="0" label="lowpass"/>
+  <int value="1" label="highpass"/>
+  <int value="2" label="bandpass"/>
+  <int value="3" label="lowshelf"/>
+  <int value="4" label="highshelf"/>
+  <int value="5" label="peaking"/>
+  <int value="6" label="notch"/>
+  <int value="7" label="allpass"/>
+</enum>
+
 <enum name="BlacklistedVideoCaptureDeviceNames" type="int">
   <int value="0" label="Google GTalk Camera Adapter"/>
   <int value="1" label="IP Camera"/>
@@ -83307,6 +83428,11 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="8" label="Unknown"/>
 </enum>
 
+<enum name="PanningModelType" type="int">
+  <int value="0" label="equalpower"/>
+  <int value="1" label="HRTF"/>
+</enum>
+
 <enum name="ParsedCookieStatus" type="int">
   <obsolete>
     Deprecated as of 9/2013. Experiment to measure control characters in cookies