Adding supported checks for WebGL

tests/html/webgl_1_test.dart

-library WebGL1Test;
+// Copyright (c) 2013, 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 web_gl_test;
 import '../../pkg/unittest/lib/unittest.dart';
-import '../../pkg/unittest/lib/html_config.dart';
+import '../../pkg/unittest/lib/html_individual_config.dart';
 import 'dart:html';
 
 // Test that WebGL is present in dart:html API
 
 main() {
-  useHtmlConfiguration();
+  useHtmlIndividualConfiguration();
 
-  test('simple', () {
-      var canvas = document.createElement("canvas");
-      var gl = canvas.getContext("experimental-webgl");
-      var shader = gl.createShader(WebGLRenderingContext.VERTEX_SHADER);
-      gl.shaderSource(shader, "void main() { }");
-      gl.compileShader(shader);
-      var success =
-          gl.getShaderParameter(shader, WebGLRenderingContext.COMPILE_STATUS);
-      expect(success, isTrue);
+  group('supported', () {
+    test('supported', () {
+      expect(WebGLRenderingContext.supported, isTrue);
+    });
+  });
+
+  group('functional', () {
+    test('unsupported fails', () {
+      var canvas = new CanvasElement();
+      var gl = canvas.getContext3d();
+      if (WebGLRenderingContext.supported) {
+        expect(gl, isNotNull);
+        expect(gl, new isInstanceOf<WebGLRenderingContext>());
+      } else {
+        expect(gl, isNull);
+      }
+    });
+
+    if (WebGLRenderingContext.supported) {
+      test('simple', () {
+        var canvas = new CanvasElement();
+        var gl = canvas.getContext('experimental-webgl');
+        var shader = gl.createShader(WebGLRenderingContext.VERTEX_SHADER);
+        gl.shaderSource(shader, 'void main() { }');
+        gl.compileShader(shader);
+        var success =
+            gl.getShaderParameter(shader, WebGLRenderingContext.COMPILE_STATUS);
+        expect(success, isTrue);
+      });
+
+      test('getContext3d', () {
+        var canvas = new CanvasElement();
+        var gl = canvas.getContext3d();
+        expect(gl, isNotNull);
+        expect(gl, new isInstanceOf<WebGLRenderingContext>());
+
+        gl = canvas.getContext3d(depth: false);
+        expect(gl, isNotNull);
+        expect(gl, new isInstanceOf<WebGLRenderingContext>());
+      });
+    }
   });
 }