Structured cloning: improve DataCloneError reporting.

LayoutTests/fast/events/message-port-multi-expected.txt

Index: LayoutTests/fast/events/message-port-multi-expected.txt
diff --git a/LayoutTests/fast/events/message-port-multi-expected.txt b/LayoutTests/fast/events/message-port-multi-expected.txt
index 80fe1f8d90a2ae02b1912a8660a4dc0689568b6c..6cc2ff60d7bbe83b3ef54fa5f86e32e5c321db0d 100644
--- a/LayoutTests/fast/events/message-port-multi-expected.txt
+++ b/LayoutTests/fast/events/message-port-multi-expected.txt
@@ -3,13 +3,13 @@ This test checks the various use cases around sending multiple ports through Mes
 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
 
 
-PASS channel.port1.postMessage("same port", [channel.port1]) threw exception DataCloneError: Failed to execute 'postMessage' on 'MessagePort': Item #0 in the array of ports contains the source port..
-PASS channel.port1.postMessage("null port", [channel3.port1, null, channel3.port2]) threw exception DataCloneError: An object could not be cloned..
-PASS channel.port1.postMessage("notAPort", [channel3.port1, {}, channel3.port2]) threw exception DataCloneError: An object could not be cloned..
-PASS channel.port1.postMessage("duplicate port", [channel3.port1, channel3.port1]) threw exception DataCloneError: An object could not be cloned..
+PASS channel.port1.postMessage("same port", [channel.port1]) threw exception DataCloneError: Failed to execute 'postMessage' on 'MessagePort': Port at index 0 contains the source port..
+PASS channel.port1.postMessage("null port", [channel3.port1, null, channel3.port2]) threw exception DataCloneError: Failed to execute 'postMessage' on 'MessagePort': Value at index 1 is an untransferable 'null' value..
+PASS channel.port1.postMessage("notAPort", [channel3.port1, {}, channel3.port2]) threw exception DataCloneError: Failed to execute 'postMessage' on 'MessagePort': Value at index 1 does not have a transferable type..
+PASS channel.port1.postMessage("duplicate port", [channel3.port1, channel3.port1]) threw exception DataCloneError: Failed to execute 'postMessage' on 'MessagePort': Message port at index 1 is a duplicate of an earlier port..
 PASS channel.port1.postMessage("notAnArray", channel3.port1) threw exception TypeError: Failed to execute 'postMessage' on 'MessagePort': The 2nd argument is neither an array, nor does it have indexed properties..
-PASS channel.port1.postMessage("notASequence", [{length: 3}]) threw exception DataCloneError: An object could not be cloned..
-PASS channel.port1.postMessage("largeSequence", largePortArray) threw exception DataCloneError: An object could not be cloned..
+PASS channel.port1.postMessage("notASequence", [{length: 3}]) threw exception DataCloneError: Failed to execute 'postMessage' on 'MessagePort': Value at index 0 does not have a transferable type..
+PASS channel.port1.postMessage("largeSequence", largePortArray) threw exception DataCloneError: Failed to execute 'postMessage' on 'MessagePort': Value at index 0 is an untransferable 'undefined' value..
 PASS successfullyParsed is true
 
 TEST COMPLETE
@@ -17,10 +17,10 @@ PASS event.ports is non-null and zero length when no port sent
 PASS event.ports is non-null and zero length when empty array sent
 PASS event.ports contains two ports when two ports sent
 PASS event.ports contains two ports when two ports re-sent after error
-PASS Sending host object has thrown DataCloneError: An object could not be cloned.
-PASS Sending host object has thrown DataCloneError: An object could not be cloned.
-PASS Sending Function object has thrown DataCloneError: An object could not be cloned.
-PASS Sending Error object has thrown DataCloneError: An object could not be cloned.
+PASS Sending host object has thrown DataCloneError: Failed to execute 'postMessage' on 'MessagePort': An object could not be cloned.
+PASS Sending host object has thrown DataCloneError: Failed to execute 'postMessage' on 'MessagePort': An object could not be cloned.
+PASS Sending Function object has thrown DataCloneError: Failed to execute 'postMessage' on 'MessagePort': An object could not be cloned.
+PASS Sending Error object has thrown DataCloneError: Failed to execute 'postMessage' on 'MessagePort': An object could not be cloned.
 PASS send-port: transferred one port
 PASS send-port-twice: transferred one port twice
 PASS send-two-ports: transferred two ports