AudioBufferSourceNode.buffer can only be set once.

Source/core/frame/UseCounter.cpp

Index: Source/core/frame/UseCounter.cpp
diff --git a/Source/core/frame/UseCounter.cpp b/Source/core/frame/UseCounter.cpp
index db331e431f557b38da086cfd871119021ff6eb33..c0f76a716c25d8d8fad864d87ab5d28365cb7bd0 100644
--- a/Source/core/frame/UseCounter.cpp
+++ b/Source/core/frame/UseCounter.cpp
@@ -838,6 +838,9 @@ String UseCounter::deprecationMessage(Feature feature)
     case CanPlayTypeKeySystem:
         return "canPlayType()'s 'keySystem' parameter is deprecated and will be removed soon. Please use 'navigator.requestMediaKeySystemAccess()' instead.";
 
+    case AudioBufferSourceBufferOnce:
+        return "Setting AudioBufferSourceNode.buffer more than once is deprecated and will no longer work in Chrome 43.";
+
     // Features that aren't deprecated don't have a deprecation message.
     default:
         return String();