Lazy initialization of the rendering thread in OfflineAudioContext

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

 /*
  * Copyright (C) 2012, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
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  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 194 matching lines @@
                              "cannot call startRendering more than once"));
   }
 
   DCHECK(!is_rendering_started_);
 
   complete_resolver_ = ScriptPromiseResolver::Create(script_state);
 
   // Start rendering and return the promise.
   is_rendering_started_ = true;
   SetContextState(kRunning);
+  DestinationHandler().InitializeOfflineRenderThread();
   DestinationHandler().StartRendering();
 
   return complete_resolver_->Promise();
 }
 
 ScriptPromise OfflineAudioContext::suspendContext(ScriptState* script_state) {
   LOG(FATAL) << "This CANNOT be called on OfflineAudioContext; this is only to "
                 "implement the pure virtual interface from BaseAudioContext.";
   return ScriptPromise();
 }
 
 ScriptPromise OfflineAudioContext::suspendContext(ScriptState* script_state,
                                                   double when) {
   DCHECK(IsMainThread());
 
   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;
   }
 
   // The specified suspend time is negative; reject the promise.
   if (when < 0) {
     resolver->Reject(DOMException::Create(
         kInvalidStateError,
         "negative suspend time (" + String::Number(when) + ") is not allowed"));
@@ skipping 207 matching lines @@
 
   // Note that the GraphLock is required before this check. Since this needs
   // to run on the audio thread, OfflineGraphAutoLocker must be used.
   if (scheduled_suspends_.Contains(CurrentSampleFrame()))
     return true;
 
   return false;
 }
 
 }  // namespace blink