Force named arguments in constructors.

lib/html/dart2js/html_dart2js.dart

Index: lib/html/dart2js/html_dart2js.dart
diff --git a/lib/html/dart2js/html_dart2js.dart b/lib/html/dart2js/html_dart2js.dart
index 5f30a82a87821f8d070051065a1ee63652109026..5d14f2c68b10480681f4de792ea10fd4b42db41a 100644
--- a/lib/html/dart2js/html_dart2js.dart
+++ b/lib/html/dart2js/html_dart2js.dart
@@ -100,7 +100,7 @@ class _AbstractWorkerEventsImpl extends _EventsImpl implements AbstractWorkerEve
 /// @domName HTMLAnchorElement
 abstract class AnchorElement implements Element {
 
-  factory AnchorElement([String href]) {
+  factory AnchorElement({String href}) {
     if (!?href) {
       return _Elements.createAnchorElement();
     }
@@ -7271,7 +7271,7 @@ class _CSSValueListImpl extends _CSSValueImpl implements List<CSSValue>, JavaScr
 /// @domName HTMLCanvasElement
 abstract class CanvasElement implements Element {
 
-  factory CanvasElement([int width, int height]) {
+  factory CanvasElement({int width, int height}) {
     if (!?width) {
       return _Elements.createCanvasElement();
     }
@@ -16616,7 +16616,7 @@ class _ImageDataImpl implements ImageData native "*ImageData" {
 /// @domName HTMLImageElement
 abstract class ImageElement implements Element {
 
-  factory ImageElement([String src, int width, int height]) {
+  factory ImageElement({String src, int width, int height}) {
     if (!?src) {
       return _Elements.createImageElement();
     }
@@ -16736,7 +16736,7 @@ class _ImageElementImpl extends _ElementImpl implements ImageElement native "*HT
 /// @domName HTMLInputElement
 abstract class InputElement implements Element {
 
-  factory InputElement([String type]) {
+  factory InputElement({String type}) {
     if (!?type) {
       return _Elements.createInputElement();
     }