More informative error messages for non-Transferables.

Elaborate the TypeError exception reported if the various
postMessage()s (on window, at the dedicated Worker global scope, or
over MessagePorts) are ill-typed transferable arguments, supplying an
error message indicating that the transferable argument isn't a
sequence type.

R=
BUG=308730

Review URL: https://codereview.chromium.org/30673002

git-svn-id: svn://svn.chromium.org/blink/trunk@160323 bbb929c8-8fbe-4397-9dbb-9b2b20218538