Fix AudioNode.disconnect() to support selective disconnection.

LayoutTests/webaudio/resources/audio-testing.js

 if (window.testRunner)
     testRunner.overridePreference("WebKitWebAudioEnabled", "1");
 
 function writeString(s, a, offset) {
     for (var i = 0; i < s.length; ++i) {
         a[offset + i] = s.charCodeAt(i);
     }
 }
 
 function writeInt16(n, a, offset) {
@@ skipping 157 matching lines @@
     var endFrame = timeToSampleFrame(grainOffset + duration, sampleRate);
 
     return endFrame - startFrame;
 }
 
 // True if the number is not an infinity or NaN
 function isValidNumber(x) {
     return !isNaN(x) && (x != Infinity) && (x != -Infinity);
 }
 
-function shouldThrowTypeError(func, text) {
-    var ok = false;
-    try {
-        func();
-    } catch (e) {
-        if (e instanceof TypeError) {
-            ok = true;
-        }
-    }
-    if (ok) {
-        testPassed(text + " threw TypeError.");
-    } else {
-        testFailed(text + " should throw TypeError.");
-    }
-}
-
 // |Audit| is a task runner for web audio test. It makes asynchronous web audio
 // testing simple and manageable.
 //
 // EXAMPLE:
 //
 //   var audit = Audit.createTaskRunner();
 //   // Define test routine. Make sure to call done() when reached at the end.
 //   audit.defineTask('foo', function (done) {
 //     var context = new AudioContext();
 //     // do things
@@ skipping 44 matching lines @@
         // Start task 0.
         this.tasks[this.queue[this.currentTask]](done);
     };
 
     return {
         createTaskRunner: function () {
             return new Tasks();
         }
     };
 
-})();
+})();
+
+
+// Create an AudioBuffer for test verification. Fill an incremental index value
+// into the each channel in the buffer. The channel index is between 1 and
+// |numChannels|. For example, a 4-channel buffer created by this function will
+// contain values 1, 2, 3 and 4 for each channel respectively.
+function createTestingBuffer(context, numChannels, length) {
+    var buffer = context.createBuffer(numChannels, length, context.sampleRate);
+    for (var i = 1; i <= numChannels; i++) {
+        var data = buffer.getChannelData(i-1);
+        for (var j = 0; j < data.length; j++) {
+            // Storing channel index into the channel buffer.
+            data[j] = i;
+        }
+    }
+    return buffer;
+}
+
+// Returns a truncated string out of a function. This is to generate a brief
+// description of function when throwing an error/exception message.
+function getTaskSummary(func) {
+    var content = func.toString().replace(/(\s|\t|\r\n|\n|\r)/gm, '');

[Raymond Toy, 2015/02/12 19:45:53]

Is this going to do something sensible if the func has a string in it? I think
not.

[hongchan, 2015/02/13 01:16:57]

It works well with the single quote and Google JS guide suggests all strings in
JS code should use the single quote. Note that we have same issues with eval().

[Raymond Toy, 2015/02/13 17:16:44]

That's going to be hard for me to get used to (single quotes).  What is the
issue with eval()?

+    return '"' + content.slice(11, -2) + '"';

[Raymond Toy, 2015/02/12 19:45:53]

What if the function is many, many lines long?  Do we really want that as the
summary?  And what are these magic numbers?

[hongchan, 2015/02/13 01:16:57]

I can't cover the multiline function. Would you rather like to specify a task
with a string? As in dom-exception.html, many exception checks are single-line
statement. If I have to put additional description just to support multi-line
function, I am not sure if we want to keep this exception check in the utility.
Probably using the original 'shouldThrow' with eval() would be better.

11 and -2 is to remove 'function(){' and ';}' from the string. It's to make the
test report cleaner.

[Raymond Toy, 2015/02/13 17:16:44]

Multiline is ok.  I'm not sure I like squashing all whitespace to nothing.  What
if the function had something like foo("a b c"). The output would be foo("abc"),
right?  That would be wrong.

I'm also pretty sure we don't want to spend too much effort trying to parse the
output of toString().
Add a comment about that.

+}
+
+// The name space for |Should| test utility. Dependencies: testPassed(),
+// testFailed() from resources/js-test.js
+var Should = {};
+
+// Expect an exception to be thrown with a certain type.
+Should.throwWithType = function (type, func) {
+    var summary = getTaskSummary(func);
+    try {
+        func();
+        testFailed(summary + ' should throw ' + type + '.');
+    } catch (e) {
+        if (e.name === type)
+            testPassed(summary + ' threw exception ' + e.name + '.');
+        else
+            testFailed(summary + ' should throw ' + type + '. Threw exception ' + e.name + '.');
+    }
+};
+
+// Expect not to throw an exception.
+Should.notThrow = function (func) {
+    var summary = getTaskSummary(func);
+    try {
+        func();
+        testPassed(summary + ' did not throw exception.');
+    } catch (e) {
+        testFailed(summary + ' should not throw exception. Threw exception ' + e.name + '.');
+    }
+};
+
+
+// Verify if the channelData array contains a single constant |value|.
+Should.haveValueInChannel = function (value, channelData) {
+    var mistmatch = {};

[Raymond Toy, 2015/02/12 19:45:53]

Typo: mistmatch -> mismatch

[hongchan, 2015/02/13 01:16:57]

Oops. Fixing it.

+    for (var i = 0; i < channelData.length; i++) {
+        if (channelData[i] !== value) {
+            mistmatch[i] = value;
+        }
+    }
+
+    var numberOfmistmatches = Object.keys(mistmatch).length;
+    if (numberOfmistmatches === 0) {
+        testPassed('ChannelData has expected values (' + value + ').');
+    } else {
+        testFailed(numberOfmistmatches + ' values in ChannelData are not equal to ' + value + ':');
+        for (var index in mistmatch) {
+            console.log('[' + index + '] : ' + mistmatch[index]);
+        }
+    }
+};