Limit OnData() callbacks to every 5ms for mac audio input.

media/audio/mac/audio_input_mac.cc

Index: media/audio/mac/audio_input_mac.cc
diff --git a/media/audio/mac/audio_input_mac.cc b/media/audio/mac/audio_input_mac.cc
index 69791cf11c6d65d7e07ed1fc67036d9e6fc8c6c7..e741b29617540a3fe0278586be9fcd78dbe7b289 100644
--- a/media/audio/mac/audio_input_mac.cc
+++ b/media/audio/mac/audio_input_mac.cc
@@ -197,17 +197,15 @@ void PCMQueueInAudioInputStream::HandleInputBuffer(
     // back to back once that internal buffer is filled.  When this happens the
     // renderer client does not have enough time to read data back from the
     // shared memory before the next write comes along.  If HandleInputBuffer()
-    // is called too frequently, Sleep() to simulate realtime input and ensure
-    // the shared memory doesn't get trampled.
+    // is called too frequently, Sleep() at least 5ms to ensure the shared
+    // memory doesn't get trampled.
     // TODO(dalecurtis): This is a HACK.  Long term the AudioQueue path is going
     // away in favor of the AudioUnit based AUAudioInputStream().  Tracked by
-    // http://crbug.com/161383
+    // http://crbug.com/161383.
     base::TimeDelta elapsed = base::Time::Now() - last_fill_;
-    base::TimeDelta buffer_length = base::TimeDelta::FromMilliseconds(
-       audio_buffer->mAudioDataByteSize * base::Time::kMillisecondsPerSecond /
-       static_cast<float>(format_.mBytesPerFrame * format_.mSampleRate));
-    if (elapsed < buffer_length)
-      base::PlatformThread::Sleep(buffer_length - elapsed);
+    const base::TimeDelta kMinDelay = base::TimeDelta::FromMilliseconds(5);
+    if (elapsed < kMinDelay)
+      base::PlatformThread::Sleep(kMinDelay - elapsed);
 
     callback_->OnData(this,
                       reinterpret_cast<const uint8*>(audio_buffer->mAudioData),