Fix AudioNode.disconnect() to support selective disconnection.

LayoutTests/webaudio/audionode-disconnect-expected.txt

Index: LayoutTests/webaudio/audionode-disconnect-expected.txt
diff --git a/LayoutTests/webaudio/audionode-disconnect-expected.txt b/LayoutTests/webaudio/audionode-disconnect-expected.txt
new file mode 100644
index 0000000000000000000000000000000000000000..f0d6e0ee8599cd9eb64cae8920f45908446fc897
--- /dev/null
+++ b/LayoutTests/webaudio/audionode-disconnect-expected.txt
@@ -0,0 +1,22 @@
+Test disconnect() method.
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+PASS ChannelData has expected values.
+PASS IndexSizeError was thrown as expected.

[Raymond Toy, 2015/02/11 21:31:18]

General comment.  The old shouldThrow methods from js-test.js had the nice
advantage of printing out what was being tested.  Now we get a stream of tests
that an appropriate error was thrown, which isn't really informative when
reading the expected results.

Perhaps your methods should add another argument to include a (short)
descriptive string that is printed out with the messages?

[hongchan, 2015/02/12 18:38:00]

A good idea. I will make it print out the summary of the task (function
argument).

+PASS Error was not thrown as expected.
+PASS ChannelData has expected values.
+PASS InvalidAccessError was thrown as expected.
+PASS InvalidAccessError was thrown as expected.
+PASS ChannelData has expected values.
+PASS IndexSizeError was thrown as expected.
+PASS InvalidAccessError was thrown as expected.
+PASS ChannelData has expected values.
+PASS InvalidAccessError was thrown as expected.
+PASS IndexSizeError was thrown as expected.
+PASS ChannelData has expected values.
+PASS ChannelData has expected values.
+PASS successfullyParsed is true
+
+TEST COMPLETE
+