Fix broken Promise-related layout tests.

LayoutTests/fast/canvas/resources/canvas-createImageBitmap-invalid-args-in-workers.js

 importScripts('../../../resources/js-test.js');
 
 self.jsTestIsAsync = true;
 
 description('Test createImageBitmap with invalid arguments in workers.');
 
+var reason;
+
+function shouldBeRejected(promise, message) {
+    return promise.then(function() {
+        testFailed('Resolved unexpectedly: ' + message);
+    }, function(e) {
+        reason = e;
+        testPassed('Rejected as expected: ' + message);
+        shouldBeTrue('reason instanceof Error');
+        debug(String(e));
+    });
+}
+
 var data;
 
 self.addEventListener('message', function(e) {
-  data = e.data;
-  shouldThrow("createImageBitmap(null, 0, 0, 10, 10)");
-  shouldThrow("createImageBitmap(data, 0, 0, 10, 0)");
-  shouldThrow("createImageBitmap(data, 0, 0, 0, 10)");
-  finishJSTest();
+    data = e.data;
+    Promise.resolve().then(function() {
+        return shouldBeRejected(createImageBitmap(null, 0, 0, 10, 10), 'null');
+    }).then(function() {
+        return shouldBeRejected(createImageBitmap(data, 0, 0, 10, 0), 'invalid area');
+    }).then(function() {
+        return shouldBeRejected(createImageBitmap(data, 0, 0, 0, 10), 'invalid area');
+    }).catch(function(e) {
+        testFailed('Unexpected rejection: ' + e);
+    }).then(finishJSTest, finishJSTest);
 });