Make KeyboardEvent cross-browser consistent.

sdk/lib/html/src/dartium_KeyEvent.dart

+/**
+ * A custom KeyboardEvent that attempts to eliminate cross-browser
+ * inconsistencies, and also provide both keyCode and charCode information
+ * for all key events (when such information can be determined).
+ *
+ * This class is very much a work in progress, and we'd love to get information
+ * on how we can make this class work with as many international keyboards as
+ * possible. Bugs welcome!
+ */
+class KeyEvent implements KeyboardEvent {
+  /** The parent KeyboardEvent that this KeyEvent is wrapping and "fixing". */
+  KeyboardEvent _parent;
+
+  /** The "fixed" value of whether the alt key is being pressed. */
+  bool _shadowAltKey;
+
+  /** Caculated value of what the estimated charCode is for this event. */
+  int _shadowCharCode;
+
+  /** Caculated value of what the estimated keyCode is for this event. */
+  int _shadowKeyCode;
+
+  /** Caculated value of what the estimated keyCode is for this event. */
+  int get keyCode => _shadowKeyCode;
+
+  /** Caculated value of what the estimated charCode is for this event. */
+  int get charCode => this.type == 'keypress' ? _shadowCharCode : 0;
+
+  /** Caculated value of whether the alt key is pressed is for this event. */
+  bool get altKey => _shadowAltKey;
+
+  /** Caculated value of what the estimated keyCode is for this event. */
+  int get which => keyCode;
+
+  /** Accessor to the underlying keyCode value is the parent event. */
+  int get _realKeyCode => _parent.keyCode;
+  
+  /** Accessor to the underlying charCode value is the parent event. */
+  int get _realCharCode => _parent.charCode;
+
+  /** Accessor to the underlying altKey value is the parent event. */
+  bool get _realAltKey => _parent.altKey;
+
+  /** Construct a KeyEvent with [parent] as event we're emulating. */
+  KeyEvent(KeyboardEvent parent) {
+    _parent = parent;
+    _shadowAltKey = _realAltKey;
+    _shadowCharCode = _realCharCode;
+    _shadowKeyCode = _realKeyCode;
+  }
+ 
+  /**
+   * Catch-all to behave for all other methods not defined here just like the
+   * _parent.
+   */
+  void noSuchMethod(InvocationMirror invocation) {
+    invocation.invokeOn(_parent);
+  }
+  String get _shadowKeyIdentifier => _parent.$dom_keyIdentifier;
+}