Support sample rates up to 384 kHz.

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

Index: third_party/WebKit/Source/modules/webaudio/BaseAudioContext.cpp
diff --git a/third_party/WebKit/Source/modules/webaudio/BaseAudioContext.cpp b/third_party/WebKit/Source/modules/webaudio/BaseAudioContext.cpp
index 2d1e489aa55875d48d66576e229779f104f79649..13f577e2df2176cdf6b5f5e9eccc9f458a9b47ca 100644
--- a/third_party/WebKit/Source/modules/webaudio/BaseAudioContext.cpp
+++ b/third_party/WebKit/Source/modules/webaudio/BaseAudioContext.cpp
@@ -253,7 +253,7 @@ AudioBuffer* BaseAudioContext::createBuffer(unsigned numberOfChannels, size_t nu
         // AudioUtilities::maxAudioBufferSampleRate().  The number of buckets is
         // fairly arbitrary.
         DEFINE_STATIC_LOCAL(CustomCountHistogram, audioBufferSampleRateHistogram,
-            ("WebAudio.AudioBuffer.SampleRate", 3000, 192000, 60));
+            ("WebAudio.AudioBuffer.SampleRate384k", 3000, 384000, 60));
 
         audioBufferChannelsHistogram.sample(numberOfChannels);
         audioBufferLengthHistogram.count(numberOfFrames);
@@ -265,12 +265,12 @@ AudioBuffer* BaseAudioContext::createBuffer(unsigned numberOfChannels, size_t nu
         // integer.  If the context is closed, don't record this because we
         // don't have a sample rate for closed context.
         if (!isContextClosed()) {
-            // The limits are choosen from 100*(3000/192000) = 1.5625 and
-            // 100*(192000/3000) = 6400, where 3000 and 192000 are the current
+            // The limits are choosen from 100*(3000/384000) = 0.78125 and
+            // 100*(384000/3000) = 12800, where 3000 and 384000 are the current
             // min and max sample rates possible for an AudioBuffer.  The number
             // of buckets is fairly arbitrary.
             DEFINE_STATIC_LOCAL(CustomCountHistogram, audioBufferSampleRateRatioHistogram,
-                ("WebAudio.AudioBuffer.SampleRateRatio", 1, 6400, 50));
+                ("WebAudio.AudioBuffer.SampleRateRatio384K", 0, 12800, 50));

[Mark P, 2016/09/15 23:16:31]

Min of histogram should always be "1".  There will always be a "underflow"
bucket to catch 0s (and negative values) that's not included in the min.

[Raymond Toy, 2016/10/10 16:28:32]

Done.

             float ratio = 100 * sampleRate / this->sampleRate();
             audioBufferSampleRateRatioHistogram.count(static_cast<int>(0.5 + ratio));
         }