Treat a stopped AudioContext as closed.

Source/modules/webaudio/OfflineAudioContext.cpp

Index: Source/modules/webaudio/OfflineAudioContext.cpp
diff --git a/Source/modules/webaudio/OfflineAudioContext.cpp b/Source/modules/webaudio/OfflineAudioContext.cpp
index b79d2e5d259e5b22a4e383ac40f362a34e7231f1..6795d97eb8038e8ff10948ac455bc152bbafe2e3 100644
--- a/Source/modules/webaudio/OfflineAudioContext.cpp
+++ b/Source/modules/webaudio/OfflineAudioContext.cpp
@@ -99,8 +99,18 @@ OfflineAudioContext::~OfflineAudioContext()
 {
 }
 
-ScriptPromise OfflineAudioContext::startOfflineRendering(ScriptState* scriptState)
+ScriptPromise OfflineAudioContext::startOfflineRendering(ScriptState* scriptState, ExceptionState& exceptionState)

[Raymond Toy, 2015/04/29 15:54:42]

Why is exceptionState needed here? It doesn't seem to be used in this function.

 {
+    // Calling close() on an OfflineAudioContext is not supported/allowed,
+    // but it might well have been stopped by its execution context.
+    if (isContextClosed()) {
+        return ScriptPromise::rejectWithDOMException(
+            scriptState,
+            DOMException::create(
+                InvalidStateError,
+                "cannot call startRendering on an OfflineAudioContext in a stopped state."));
+    }
+
     if (m_offlineResolver) {
         // Can't call startRendering more than once.  Return a rejected promise now.
         return ScriptPromise::rejectWithDOMException(