Expire OfflineAudioContext histograms

Remove the histogram WebAudio.OfflineAudioContext.SampleRate384kHz.

Also removing OAC.ChannelCount, and OAC.Length since they all go with
SampleRate384kHz and there's no point in keeping these if one of them
is expired.

Bug: 1165240
Change-Id: I9dcb3ea66ba4ba7704e0bbf1164a9cf0d5a395da
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2625378Reviewed-by: Hongchan Choi <hongchan@chromium.org>
Reviewed-by: Weilun Shi <sweilun@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Raymond Toy <rtoy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843025}

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

@@ -108,21 +108,6 @@ OfflineAudioContext* OfflineAudioContext::Create(
   fprintf(stderr, "[%16p]: OfflineAudioContext::OfflineAudioContext()\n",
           audio_context);
 #endif
-  base::UmaHistogramSparse("WebAudio.OfflineAudioContext.ChannelCount",
-                           number_of_channels);
-  // Arbitrarly limit the maximum length to 1 million frames (about 20 sec
-  // at 48kHz).  The number of buckets is fairly arbitrary.
-  base::UmaHistogramCounts1M("WebAudio.OfflineAudioContext.Length",
-                             number_of_frames);
-  // The limits are the min and max AudioBuffer sample rates currently
-  // supported.  We use explicit values here instead of
-  // audio_utilities::minAudioBufferSampleRate() and
-  // audio_utilities::maxAudioBufferSampleRate().  The number of buckets is
-  // fairly arbitrary.
-  base::UmaHistogramCustomCounts(
-      "WebAudio.OfflineAudioContext.SampleRate384kHz", sample_rate, 3000,
-      384000, 50);
-
   return audio_context;
 }
 

tools/metrics/histograms/histograms_xml/web_audio/histograms.xml

@@ -223,6 +223,9 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 
 <histogram name="WebAudio.OfflineAudioContext.ChannelCount" units="units"
     expires_after="2021-07-06">
+  <obsolete>
+    Removed 2021-01-12. See crbug.com/1165240.
+  </obsolete>
   <owner>rtoy@chromium.org</owner>
   <owner>hongchan@chromium.org</owner>
   <summary>
@@ -234,6 +237,9 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 
 <histogram name="WebAudio.OfflineAudioContext.Length" units="frames"
     expires_after="2021-05-23">
+  <obsolete>
+    Removed 2021-01-12. See crbug.com/1165240.
+  </obsolete>
   <owner>rtoy@chromium.org</owner>
   <owner>hongchan@chromium.org</owner>
   <summary>
@@ -245,6 +251,9 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 
 <histogram name="WebAudio.OfflineAudioContext.SampleRate384kHz" units="Hz"
     expires_after="2021-02-18">
+  <obsolete>
+    Removed 2021-01-12. See crbug.com/1165240.
+  </obsolete>
   <owner>rtoy@chromium.org</owner>
   <owner>hongchan@chromium.org</owner>
   <summary>