Added tests to previously broken functionality and added null checks.

sdk/lib/html/dart2js/html_dart2js.dart

Index: sdk/lib/html/dart2js/html_dart2js.dart
diff --git a/sdk/lib/html/dart2js/html_dart2js.dart b/sdk/lib/html/dart2js/html_dart2js.dart
index 3bb3ec27a797671c48c9f6109aa6f4a086238033..56cfd19145364c2af42d2c36e19d47c792498e15 100644
--- a/sdk/lib/html/dart2js/html_dart2js.dart
+++ b/sdk/lib/html/dart2js/html_dart2js.dart
@@ -1211,9 +1211,11 @@ class CanvasRenderingContext2D extends CanvasRenderingContext native "CanvasRend
       _putImageData_1(imagedata_1, dx, dy);
       return;
     }
-    var imagedata_2 = _convertDartToNative_ImageData(imagedata);
-    _putImageData_2(imagedata_2, dx, dy, dirtyX, dirtyY, dirtyWidth, dirtyHeight);
-    return;
+    if (dirtyX != null && dirtyY != null && dirtyWidth != null && dirtyHeight != null) {
+      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')
@@ -1306,9 +1308,11 @@ class CanvasRenderingContext2D extends CanvasRenderingContext native "CanvasRend
       _putImageDataHD_1(imagedata_1, dx, dy);
       return;
     }
-    var imagedata_2 = _convertDartToNative_ImageData(imagedata);
-    _putImageDataHD_2(imagedata_2, dx, dy, dirtyX, dirtyY, dirtyWidth, dirtyHeight);
-    return;
+    if (dirtyX != null && dirtyY != null && dirtyWidth != null && dirtyHeight != null) {
+      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')