AudioBufferSourceNode loop duration should be the actual duration

LayoutTests/webaudio/resources/audiobuffersource-testing.js

 function createTestBuffer(context, sampleFrameLength) {
     var audioBuffer = context.createBuffer(1, sampleFrameLength, context.sampleRate);
     var channelData = audioBuffer.getChannelData(0);
 
     // Create a simple linear ramp starting at zero, with each value in the buffer equal to its index position.
     for (var i = 0; i < sampleFrameLength; ++i)
         channelData[i] = i;
 
     return audioBuffer;
 }
@@ skipping 11 matching lines @@
         description = test.description;
     } else {
         // No description given, so create a basic one from the given test parameters.
         description = "loop from " + test.loopStartFrame + " -> " + test.loopEndFrame;
         if (test.offsetFrame)
             description += " with offset " + test.offsetFrame;
         if (test.playbackRate && test.playbackRate != 1)
             description += " with playbackRate of " + test.playbackRate;
     }
 
-    for (var j = 0; j < test.renderFrames; ++j) {
+    var framesToTest;
+
+    if (test.renderFrames)
+        framesToTest = test.renderFrames;
+    else if (test.durationFrames)
+        framesToTest = test.durationFrames;
+
+    // Verify that the output matches
+    for (var j = 0; j < framesToTest; ++j) {
         if (expected[j] != renderedData[offsetFrame + j]) {
             // Copy from Float32Array to regular JavaScript array for error message.
             var renderedArray = new Array();
             for (var j = 0; j < test.renderFrames; ++j)
                 renderedArray[j] = renderedData[offsetFrame + j];
 
             var s = description + ": expected: " + expected + " actual: " + renderedArray;
             testFailed(s);
             success = false;
             break;
         }
     }
 
+    // Verify that we get all zeroes after the buffer (or duration) has passed.
+    for (var j = framesToTest; j < testSpacingFrames; ++j) {
+        if (renderedData[offsetFrame + j]) {
+            // Copy from Float32Array to regular JavaScript array for error message.
+            var renderedArray = new Array();
+            for (var j = framesToTest; j < testSpacingFrames; ++j)
+                renderedArray[j - framesToTest] = renderedData[offsetFrame + j];
+
+            var s = description + ": expected: all zeroes actual: " + renderedArray;
+            testFailed(s);
+            success = false;
+            break;
+        }
+    }
+
     if (success)
         testPassed(description);
 
     return success;
 }
 
 function checkAllTests(event) {
     var renderedBuffer = event.renderedBuffer;
     for (var i = 0; i < tests.length; ++i)
         checkSingleTest(renderedBuffer, i);
 
     if (window.testRunner)
         testRunner.notifyDone()
 }