Revert to ? presence checks.

sdk/lib/html/dart2js/html_dart2js.dart

 /// The Dart HTML library.
 library dart.dom.html;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:_collection-dev' hide Symbol;
 import 'dart:html_common';
 import 'dart:indexed_db';
 import 'dart:isolate';
 import 'dart:json' as json;
@@ skipping 1193 matching lines @@
   void moveTo(num x, num y) native;
 
   @DomName('CanvasRenderingContext2D.putImageData')
   @DocsEditable
   void putImageData(ImageData imagedata, num dx, num dy, [num dirtyX, num dirtyY, num dirtyWidth, num dirtyHeight]) {
     if (!?dirtyX && !?dirtyY && !?dirtyWidth && !?dirtyHeight) {
       var imagedata_1 = _convertDartToNative_ImageData(imagedata);
       _putImageData_1(imagedata_1, dx, dy);
       return;
     }
-    if (dirtyX != null && dirtyY != null && dirtyWidth != null && dirtyHeight != null) {
+    if (?dirtyX && ?dirtyY && ?dirtyWidth && ?dirtyHeight) {
       var imagedata_2 = _convertDartToNative_ImageData(imagedata);
       _putImageData_2(imagedata_2, dx, dy, dirtyX, dirtyY, dirtyWidth, dirtyHeight);
       return;
     }
     throw new ArgumentError("Incorrect number or type of arguments");
   }
   @JSName('putImageData')
   @DomName('CanvasRenderingContext2D.putImageData')
   @DocsEditable
   void _putImageData_1(imagedata, dx, dy) native;
@@ skipping 76 matching lines @@
   @DocsEditable
   @SupportedBrowser(SupportedBrowser.CHROME)
   @SupportedBrowser(SupportedBrowser.SAFARI)
   @Experimental
   void putImageDataHD(ImageData imagedata, num dx, num dy, [num dirtyX, num dirtyY, num dirtyWidth, num dirtyHeight]) {
     if (!?dirtyX && !?dirtyY && !?dirtyWidth && !?dirtyHeight) {
       var imagedata_1 = _convertDartToNative_ImageData(imagedata);
       _putImageDataHD_1(imagedata_1, dx, dy);
       return;
     }
-    if (dirtyX != null && dirtyY != null && dirtyWidth != null && dirtyHeight != null) {
+    if (?dirtyX && ?dirtyY && ?dirtyWidth && ?dirtyHeight) {
       var imagedata_2 = _convertDartToNative_ImageData(imagedata);
       _putImageDataHD_2(imagedata_2, dx, dy, dirtyX, dirtyY, dirtyWidth, dirtyHeight);
       return;
     }
     throw new ArgumentError("Incorrect number or type of arguments");
   }
   @JSName('webkitPutImageDataHD')
   @DomName('CanvasRenderingContext2D.webkitPutImageDataHD')
   @DocsEditable
   @SupportedBrowser(SupportedBrowser.CHROME)
@@ skipping 27034 matching lines @@
       _position = nextPosition;
       return true;
     }
     _current = null;
     _position = _array.length;
     return false;
   }
 
   T get current => _current;
 }