Adding Angular and dependent packages for testing

third_party/pkg/angular/lib/directive/ng_style.dart

+part of angular.directive;
+
+/**
+  * The `ngStyle` directive allows you to set CSS style on an HTML element conditionally.
+  *
+  * @example
+        <span ng-style="{color:'red'}">Sample Text</span>
+  */
+@NgDirective(
+    selector: '[ng-style]',
+    map: const { 'ng-style': '@styleExpression'})
+class NgStyleDirective {
+  dom.Element _element;
+  Scope _scope;
+
+  String _styleExpression;
+
+  NgStyleDirective(this._element, this._scope);
+
+  Function _removeWatch = () => null;
+  var _lastStyles;
+
+/**
+  * ng-style attribute takes an expression hich evals to an
+  *      object whose keys are CSS style names and values are corresponding values for those CSS
+  *      keys.
+  */
+  set styleExpression(String value) {
+    _styleExpression = value;
+    _removeWatch();
+    _removeWatch = _scope.$watchCollection(_styleExpression, _onStyleChange);
+  }
+
+  _onStyleChange(Map newStyles) {
+    dom.CssStyleDeclaration css = _element.style;
+    if (_lastStyles != null) {
+      _lastStyles.forEach((val, style) { css.setProperty(val, ''); });
+    }
+    _lastStyles = newStyles;
+
+    if (newStyles != null) {
+      newStyles.forEach((val, style) { css.setProperty(val, style); });
+    }
+  }
+}