Add WebThread in AudioDestination to support AudioWorkletThread

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

Index: third_party/WebKit/Source/platform/audio/PushPullFIFO.cpp
diff --git a/third_party/WebKit/Source/platform/audio/PushPullFIFO.cpp b/third_party/WebKit/Source/platform/audio/PushPullFIFO.cpp
index fdfafd7a37b7ebf3252a98ece9924cee92556794..dca1d44c147d093559ef207ccc4cd3701063ec24 100644
--- a/third_party/WebKit/Source/platform/audio/PushPullFIFO.cpp
+++ b/third_party/WebKit/Source/platform/audio/PushPullFIFO.cpp
@@ -34,6 +34,8 @@ PushPullFIFO::~PushPullFIFO() {}
 // Push the data from |inputBus| to FIFO. The size of push is determined by
 // the length of |inputBus|.
 void PushPullFIFO::Push(const AudioBus* input_bus) {
+  MutexLocker locker(lock_);
+
   CHECK(input_bus);
   CHECK_EQ(input_bus->length(), AudioUtilities::kRenderQuantumFrames);
   SECURITY_CHECK(input_bus->length() <= fifo_length_);
@@ -82,7 +84,11 @@ void PushPullFIFO::Push(const AudioBus* input_bus) {
 
 // Pull the data out of FIFO to |outputBus|. If remaining frame in the FIFO
 // is less than the frames to pull, provides remaining frame plus the silence.
-void PushPullFIFO::Pull(AudioBus* output_bus, size_t frames_requested) {
+void PushPullFIFO::Pull(
+    AudioBus* output_bus,
+    size_t frames_requested,
+    std::unique_ptr<WTF::Function<void(size_t, size_t)>>
+        push_request_render_callback) {
 #if OS(ANDROID)
   if (!output_bus) {
     // Log when outputBus or FIFO object is invalid. (crbug.com/692423)
@@ -110,6 +116,9 @@ void PushPullFIFO::Pull(AudioBus* output_bus, size_t frames_requested) {
                  << " >= " << fifo_length_ << ")";
   }
 #endif
+
+  MutexLocker locker(lock_);
+
   CHECK(output_bus);
   SECURITY_CHECK(frames_requested <= output_bus->length());
   SECURITY_CHECK(frames_requested <= fifo_length_);
@@ -162,10 +171,20 @@ void PushPullFIFO::Pull(AudioBus* output_bus, size_t frames_requested) {
   // Update the number of frames in FIFO.
   frames_available_ -= frames_to_fill;
   DCHECK_EQ((index_read_ + frames_available_) % fifo_length_, index_write_);
+
+  // Number of frames to render via WebAudio graph. |framesToRender > 0| means
+  // the frames in FIFO is not enough to fulfill the requested frames from the
+  // audio device.
+  size_t frames_to_render = frames_requested > frames_available_
+                                ? frames_requested - frames_available_
+                                : 0;
+
+  if (frames_to_render > 0)
+    (*push_request_render_callback)(frames_requested, frames_to_render);

[nhiroki, 2017/04/17 03:27:30]

This callback is called within the mutex section (see line 120). That could be
risky, for example, some callback may wrongly call PushPullFIFO::Pull() again.

If |frames_requested| is never modified in this function and |frames_to_render|
is the only real return value, how about just returning |frames_to_render|
instead of calling a given callback?

[hongchan, 2017/04/17 16:03:29]

Actually that'd be cleaner than what I have here. I would like to know how olka@
think about this.

 }
 
 const PushPullFIFOStateForTest PushPullFIFO::GetStateForTest() const {
-  return {length(),     NumberOfChannels(), FramesAvailable(), index_read_,
+  return {length(),     NumberOfChannels(), frames_available_, index_read_,
           index_write_, overflow_count_,    underflow_count_};
 }