Use testharness.js instead of js-test.js in LayoutTests/fast/canvas tests.

third_party/WebKit/LayoutTests/fast/canvas/canvas-toBlob-invalid.html

-<script src="../../resources/js-test.js"></script>
+<script src="../../resources/testharness.js"></script>
+<script src="../../resources/testharnessreport.js"></script>
 <script type='text/javascript'>
-description("Test the handling of invalid arguments in canvas toBlob().");
+async_test(t => {
 
-if (window.testRunner) {
-    testRunner.dumpAsText();
-    testRunner.waitUntilDone();
-}
+    var numAsyncCalls = 2;
+    function finishOneAsyncCall()
+    {
+        if (--numAsyncCalls == 0)
+            t.done();
+    }
+    
+    var canvas = document.createElement('canvas');
+    var ctx = canvas.getContext("2d"); 
+    ctx.strokeStyle = "red";
+    ctx.strokeRect(0, 0, 50, 50);
+    
+    assert_throws(new TypeError(), function() {canvas.toBlob();}, "TypeError: Failed to execute 'toBlob' on 'HTMLCanvasElement': 1 argument required, but only 0 present.");

[Justin Novosad, 2017/02/16 22:32:42]

Nit: better not to use the third argument of assert_throws. It makes the test
non-interoperable and we'll be forced to update the test every time the message
text is tweaked, which is annoying.

+    assert_throws(new TypeError(), function() {canvas.toBlob(null);}, "TypeError: Failed to execute 'toBlob' on 'HTMLCanvasElement': The callback provided as parameter 1 is not a function.");
+    assert_throws(new TypeError(), function() {canvas.toBlob(undefined);}, "TypeError: Failed to execute 'toBlob' on 'HTMLCanvasElement': The callback provided as parameter 1 is not a function.");
 
-var numAsyncCalls = 2;
-function finishOneAsyncCall()
-{
-    numAsyncCalls--;
-    if (numAsyncCalls == 0 && window.testRunner) {
-        testRunner.notifyDone();
-    }
-}
-
-var canvas = document.createElement('canvas');
-var ctx = canvas.getContext("2d"); 
-ctx.strokeStyle = "red";
-ctx.strokeRect(0, 0, 50, 50);
-
-shouldThrow("canvas.toBlob();");
-shouldThrow("canvas.toBlob(null);");
-shouldThrow("canvas.toBlob(undefined);");
-// Passing the callback argument without blob handle silently fails.
-shouldNotThrow("canvas.toBlob(function() { finishOneAsyncCall(); });");
-
-// Invalid quality argument will fall back to default value
-shouldNotThrow("canvas.toBlob(function(blob) { finishOneAsyncCall(); }, 'image/jpeg', 500)");
+    // Passing the callback argument without blob handle silently fails.
+    canvas.toBlob(function() { finishOneAsyncCall(); });
+   
+    // Invalid quality argument will fall back to default value
+    canvas.toBlob(function(blob) { finishOneAsyncCall(); }, 'image/jpeg', 500);
+    
+}, "Test the handling of invalid arguments in canvas toBlob().");
 </script>