Changes to allow more precise inference of live native classes.

sdk/lib/html/src/dart2js_Conversions.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 
 // Conversions for IDBKey.
 //
 // Per http://www.w3.org/TR/IndexedDB/#key-construct
 //
 // "A value is said to be a valid key if it is one of the following types: Array
@@ skipping 43 matching lines @@
 
 class _TypedImageData implements ImageData {
   final Uint8ClampedArray data;
   final int height;
   final int width;
 
   _TypedImageData(this.data, this.height, this.width);
 }
 
 ImageData _convertNativeToDart_ImageData(nativeImageData) {
+
+  // None of the native getters that return ImageData have the type ImageData
+  // since that is incorrect for FireFox (which returns a plain Object).  So we
+  // need something that tells the compiler that the ImageData class has been
+  // instantiated.
+  // TODO(sra): Remove this when all the ImageData returning APIs have been
+  // annotated as returning the union ImageData + Object.
+  JS('ImageData', '0');
+
   if (nativeImageData is ImageData) return nativeImageData;
 
   // On Firefox the above test fails because imagedata is a plain object.
   // So we create a _TypedImageData.
 
   return new _TypedImageData(
       JS('var', '#.data', nativeImageData),
       JS('var', '#.height', nativeImageData),
       JS('var', '#.width', nativeImageData));
 }
 
 // We can get rid of this conversion if _TypedImageData implements the fields
 // with native names.
 _convertDartToNative_ImageData(ImageData imageData) {
   if (imageData is _TypedImageData) {
-    return JS('Object', '{data: #, height: #, width: #}',
+    return JS('', '{data: #, height: #, width: #}',
         imageData.data, imageData.height, imageData.width);
   }
   return imageData;
 }
 
 
 /// Converts a JavaScript object with properties into a Dart Map.
 /// Not suitable for nested objects.
 Map _convertNativeToDart_Dictionary(object) {
   if (object == null) return null;
@@ skipping 325 matching lines @@
 }
 
 
 bool _isJavaScriptDate(value) => JS('bool', '# instanceof Date', value);
 bool _isJavaScriptRegExp(value) => JS('bool', '# instanceof RegExp', value);
 bool _isJavaScriptArray(value) => JS('bool', '# instanceof Array', value);
 bool _isJavaScriptSimpleObject(value) =>
     JS('bool', 'Object.getPrototypeOf(#) === Object.prototype', value);
 bool _isImmutableJavaScriptArray(value) =>
     JS('bool', r'!!(#.immutable$list)', value);