Add WebThread in AudioDestination to support AudioWorkletThread

third_party/WebKit/Source/platform/audio/PushPullFIFO.h

Index: third_party/WebKit/Source/platform/audio/PushPullFIFO.h
diff --git a/third_party/WebKit/Source/platform/audio/PushPullFIFO.h b/third_party/WebKit/Source/platform/audio/PushPullFIFO.h
index 2341372f35ab452fb8814dc22208ff3c24e9cd87..2789dfd4da690ba14cc43b7f2e9e862e1443b563 100644
--- a/third_party/WebKit/Source/platform/audio/PushPullFIFO.h
+++ b/third_party/WebKit/Source/platform/audio/PushPullFIFO.h
@@ -8,6 +8,7 @@
 #include "platform/audio/AudioBus.h"
 #include "public/platform/WebCommon.h"
 #include "wtf/Allocator.h"
+#include "wtf/ThreadingPrimitives.h"
 
 namespace blink {
 
@@ -65,6 +66,8 @@ class BLINK_PLATFORM_EXPORT PushPullFIFO {
   const PushPullFIFOStateForTest getStateForTest() const;
 
  private:
+  Mutex m_lock;

[nhiroki, 2017/03/29 01:54:05]

What does this lock protect?

[haraken, 2017/03/29 07:56:24]

Same question from me.

[hongchan, 2017/03/29 19:39:59]

See push()/pull() methods. This lock protects:
m_fifoBus
m_indexWrite
m_indexRead
m_framesAvailable

+
   // The size of the FIFO.
   const size_t m_fifoLength = 0;