Fix the unnecessary sleep when no back to back OnData call.

media/audio/pulse/pulse_input.cc

Index: media/audio/pulse/pulse_input.cc
diff --git a/media/audio/pulse/pulse_input.cc b/media/audio/pulse/pulse_input.cc
index 4976b5610eda39d309f3a347de448a0ce9e494b2..6c9855e504c568bf47771ae04e6470c5f06ac061 100644
--- a/media/audio/pulse/pulse_input.cc
+++ b/media/audio/pulse/pulse_input.cc
@@ -281,7 +281,10 @@ void PulseAudioInputStream::ReadData() {
     hardware_delay += fifo_.GetAvailableFrames() * params_.GetBytesPerFrame();
     callback_->OnData(this, audio_bus, hardware_delay, normalized_volume);
 
-    base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(5));
+    // Sleep 5ms to wait until render consumes the data in order to avoid
+    // back to back OnData() method.
+    if (fifo_.available_blocks())
+      base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(5));
   }
 
   pa_threaded_mainloop_signal(pa_mainloop_, 0);