Lazy initialization of the rendering thread in OfflineAudioContext

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

Index: third_party/WebKit/Source/modules/webaudio/OfflineAudioContext.cpp
diff --git a/third_party/WebKit/Source/modules/webaudio/OfflineAudioContext.cpp b/third_party/WebKit/Source/modules/webaudio/OfflineAudioContext.cpp
index 1b310a9db147308bf597838d58b70511ed36e1ad..b7dcfba502017f5db926028a233f844fc4581fac 100644
--- a/third_party/WebKit/Source/modules/webaudio/OfflineAudioContext.cpp
+++ b/third_party/WebKit/Source/modules/webaudio/OfflineAudioContext.cpp
@@ -212,6 +212,7 @@ ScriptPromise OfflineAudioContext::startOfflineRendering(
   // Start rendering and return the promise.
   is_rendering_started_ = true;
   SetContextState(kRunning);
+  DestinationHandler().InitializeOfflineRenderThread();
   DestinationHandler().StartRendering();
 
   return complete_resolver_->Promise();
@@ -230,8 +231,8 @@ ScriptPromise OfflineAudioContext::suspendContext(ScriptState* script_state,
   ScriptPromiseResolver* resolver = ScriptPromiseResolver::Create(script_state);
   ScriptPromise promise = resolver->Promise();
 
-  // The render thread does not exist; reject the promise.
-  if (!DestinationHandler().OfflineRenderThread()) {
+  // If the rendering is finished, reject the promise.
+  if (ContextState() == AudioContextState::kClosed) {

[Raymond Toy, 2017/05/23 20:37:34]

Still need a test for this.

[hongchan, 2017/05/23 20:55:46]

https://cs.chromium.org/chromium/src/third_party/WebKit/LayoutTests/webaudio/...

It's already there. Functionally the task is exactly testing this code. Now
we're getting a correct error message from the test:

"PASS   Scheduling a suspend after the render completion rejected correctly with
InvalidStateError: the rendering is already finished."

So fortunately I think we just fixed the issue of the original code.

     resolver->Reject(DOMException::Create(kInvalidStateError,
                                           "the rendering is already finished"));
     return promise;