Measure length of impulse responses for ConvolverNode

Add time histogram to measure the length of the impulse response for a
ConvolverNode.

Bug: 998154
Change-Id: I8167cbfe51edea0e072ad571095c6f11d5b12526
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1773418
Commit-Queue: Raymond Toy <rtoy@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Reviewed-by: Hongchan Choi <hongchan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#701679}

third_party/blink/renderer/modules/webaudio/convolver_node.cc

@@ -31,6 +31,7 @@
 #include "third_party/blink/renderer/modules/webaudio/convolver_options.h"
 #include "third_party/blink/renderer/platform/audio/reverb.h"
 #include "third_party/blink/renderer/platform/bindings/exception_state.h"
+#include "third_party/blink/renderer/platform/instrumentation/histogram.h"
 
 // Note about empirical tuning:
 // The maximum FFT size affects reverb performance and accuracy.
@@ -134,6 +135,12 @@ void ConvolverHandler::SetBuffer(AudioBuffer* buffer,
     return;
   }
 
+  {
+    // Get some statistics on the size of the impulse response.
+    UMA_HISTOGRAM_LONG_TIMES("WebAudio.ConvolverNode.ImpulseResponseLength",
+                             base::TimeDelta::FromSecondsD(buffer->duration()));
+  }
+
   // Wrap the AudioBuffer by an AudioBus. It's an efficient pointer set and not
   // a memcpy().  This memory is simply used in the Reverb constructor and no
   // reference to it is kept for later use in that class.

tools/metrics/histograms/histograms.xml

@@ -155804,6 +155804,16 @@ regressions. -->
   </summary>
 </histogram>
 
+<histogram name="WebAudio.ConvolverNode.ImpulseResponseLength" units="ms"
+    expires_after="M82">
+  <owner>rtoy@chromium.org</owner>
+  <owner>hongchan@chromium.org</owner>
+  <summary>
+    The duration in millisec of impulse responses for a ConvolverNode. Recorded
+    each time the impulse response is set for a ConvolverNode.
+  </summary>
+</histogram>
+
 <histogram name="WebAudio.IIRFilterNode.Order" units="units"
     expires_after="M81">
   <owner>rtoy@chromium.org</owner>