Check for duplicate ArrayBuffer transferables.

LayoutTests/fast/events/resources/message-port-multi.js

 if (window.testRunner) {
     testRunner.dumpAsText();
     testRunner.waitUntilDone();
 }
 
 description("This test checks the various use cases around sending multiple ports through MessagePort.postMessage");
 
 var channel = new MessageChannel();
 var channel2 = new MessageChannel();
 var channel3 = new MessageChannel();
 var channel4 = new MessageChannel();
 
 channel.port1.postMessage("noport");
 channel.port1.postMessage("zero ports", []);
 channel.port1.postMessage("two ports", [channel2.port1, channel2.port2]);
 
 // Now test various failure cases
 shouldThrow('channel.port1.postMessage("same port", [channel.port1])', '"DataCloneError: Failed to execute \'postMessage\' on \'MessagePort\': Port at index 0 contains the source port."');
 shouldThrow('channel.port1.postMessage("null port", [channel3.port1, null, channel3.port2])', '"DataCloneError: Failed to execute \'postMessage\' on \'MessagePort\': Value at index 1 is an untransferable \'null\' value."');
 shouldThrow('channel.port1.postMessage("notAPort", [channel3.port1, {}, channel3.port2])', '"DataCloneError: Failed to execute \'postMessage\' on \'MessagePort\': Value at index 1 does not have a transferable type."');
 shouldThrow('channel.port1.postMessage("duplicate port", [channel3.port1, channel3.port1])', '"DataCloneError: Failed to execute \'postMessage\' on \'MessagePort\': Message port at index 1 is a duplicate of an earlier port."');
 // Should be OK to send channel3.port1 (should not have been disentangled by the previous failed calls).
 channel.port1.postMessage("entangled ports", [channel3.port1, channel3.port2]);
 
 shouldThrow('channel.port1.postMessage("notAnArray", channel3.port1)', '"TypeError: Failed to execute \'postMessage\' on \'MessagePort\': The 2nd argument is neither an array, nor does it have indexed properties."');
 shouldThrow('channel.port1.postMessage("notASequence", [{length: 3}])', '"DataCloneError: Failed to execute \'postMessage\' on \'MessagePort\': Value at index 0 does not have a transferable type."');
+var arrayBuffer = new ArrayBuffer(2);
+shouldThrow('channel.port1.postMessage("duplicate buffer", [arrayBuffer, arrayBuffer])', '"DataCloneError: Failed to execute \'postMessage\' on \'MessagePort\': ArrayBuffer at index 1 is a duplicate of an earlier ArrayBuffer."');
 
 // Should not crash (we should figure out that the array contains undefined
 // entries).
 var largePortArray = [];
 largePortArray[1234567890] = channel4.port1;
 shouldThrow('channel.port1.postMessage("largeSequence", largePortArray)', '"DataCloneError: Failed to execute \'postMessage\' on \'MessagePort\': Value at index 0 is an untransferable \'undefined\' value."');
 
 channel.port1.postMessage("done");
 
 function testTransfers() {
@@ skipping 100 matching lines @@
         if (event.ports.length == 2)
             testPassed("event.ports contains two ports when two ports re-sent after error");
         else
             testFailed("event.ports contained " + event.ports.length + " when two ports re-sent after error");
     } else if (event.data == "done") {
         testTransfers();
     } else
         testFailed("Received unexpected message: " + event.data);
 }