Rename context2d to context2D.

tests/html/canvasrenderingcontext2d_test.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.
 
 library canvas_rendering_context_2d_test; import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_individual_config.dart';
 import 'dart:html';
 import 'dart:math';
 
 // Some rounding errors in the browsers.
 checkPixel(List<int> pixel, List<int> expected) {
   expect(pixel[0], closeTo(expected[0], 2));
   expect(pixel[1], closeTo(expected[1], 2));
   expect(pixel[2], closeTo(expected[2], 2));
   expect(pixel[3], closeTo(expected[3], 2));
 }
 
 var canvas;
 var context;
 var otherCanvas;
 var otherContext;
 var video;
 
 void createCanvas() {
   canvas = new CanvasElement();
   canvas.width = 100;
   canvas.height = 100;
 
-  context = canvas.context2d;
+  context = canvas.context2D;
 }
 
 void createOtherCanvas() {
   otherCanvas = new CanvasElement();
   otherCanvas.width = 10;
   otherCanvas.height = 10;
-  otherContext = otherCanvas.context2d;
+  otherContext = otherCanvas.context2D;
   otherContext.fillStyle = "red";
   otherContext.fillRect(0, 0, otherCanvas.width, otherCanvas.height);
 }
 
 void setupFunc() {
   createCanvas();
   createOtherCanvas();
   video = new VideoElement();
 }
 
@@ skipping 549 matching lines @@
       var imageData = context.createImageData(15, 15);
       expect(imageData.width, 15);
       expect(imageData.height, 15);
 
       var other = context.createImageDataFromImageData(imageData);
       expect(other.width, 15);
       expect(other.height, 15);
     });
   });
 }