AudioBufferSourceNode.buffer can only be set once.

Source/modules/webaudio/AudioBufferSourceNode.cpp

Index: Source/modules/webaudio/AudioBufferSourceNode.cpp
diff --git a/Source/modules/webaudio/AudioBufferSourceNode.cpp b/Source/modules/webaudio/AudioBufferSourceNode.cpp
index 5d40b0ae4c8941d76df1b7548b4005c980e23d54..f012779991e9a4a7d5d53239c6b3ccd782be4cd6 100644
--- a/Source/modules/webaudio/AudioBufferSourceNode.cpp
+++ b/Source/modules/webaudio/AudioBufferSourceNode.cpp
@@ -340,6 +340,13 @@ void AudioBufferSourceNode::setBuffer(AudioBuffer* buffer, ExceptionState& excep
 {
     ASSERT(isMainThread());
 
+    if (m_buffer) {
+        exceptionState.throwDOMException(
+            InvalidStateError,
+            "Buffer can only be set once");
+        return;
+    }
+
     // The context must be locked since changing the buffer can re-configure the number of channels that are output.

[Ken Russell (switch to Gerrit), 2015/01/20 21:26:16]

This comment, and probably later ones, should be updated.

[Raymond Toy, 2015/01/20 21:35:03]

I believe this is still true.  On creation without a buffer, the
AudioBufferSource is configured for a single channel (of silence).  When the
buffer is assigned, the source node reconfigures the number of channels to match
the buffer.

     AudioContext::AutoLocker contextLocker(context());