Copy lib/dom tests that use dart:html to lib/html.

tests/dom/webgl_1_test.dart

-#library('WebGL1Test');
-#import('../../lib/unittest/unittest.dart');
-#import('../../lib/unittest/html_config.dart');
-#import('dart:html');
-
-// Test that WebGL is present in dart:html API
-
-main() {
-  useHtmlConfiguration();
-
-  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.isTrue(success);
-  });
-}