Updating Element.scrollIntoView to be platform independent.

tools/dom/templates/html/impl/impl_Element.darttemplate

 // 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.
 
 part of $LIBRARYNAME;
 
 // TODO(jacobr): use _Lists.dart to remove some of the duplicated
 // functionality.
 class _ChildrenElementList implements List {
   // Raw Element.
@@ skipping 751 matching lines @@
    * deprecated and will simply return this [Element] object.
    *
    * [wc]: http://dvcs.w3.org/hg/webcomponents/raw-file/tip/explainer/index.html
    * [x-tags]: http://x-tags.org/
    */
 $if DART2JS
   @Creates('Null')  // Set from Dart code; does not instantiate a native type.
 $endif
   var xtag;
 
+  /**
+   * Scrolls this element into view.
+   *
+   * Only one of of the alignment options may be specified at a time.
+   *
+   * If no options are specified then this will attempt to scroll the minimum
+   * amount needed to bring the element into view.
+   *
+   * Note that alignCenter is currently only supported on WebKit platforms. If
+   * alignCenter is specified but not supported then this will fall back to
+   * alignTop.
+   *
+   * See also:
+   *
+   * * [scrollIntoView](http://docs.webplatform.org/wiki/dom/methods/scrollIntoView)
+   * * [scrollIntoViewIfNeeded](http://docs.webplatform.org/wiki/dom/methods/scrollIntoViewIfNeeded)
+   */
+  void scrollIntoView({bool alignCenter, bool alignTop, bool alignBottom}) {

[Jacob, 2013/02/12 23:12:33]

shouldn't this be an enum instead of 3 bools?

+    var paramCount = (alignCenter != null ? 1 : 0) +
+        (alignTop != null ? 1 : 0) + (alignBottom != null ? 1 : 0);
+    if (paramCount > 1) {
+      throw new ArgumentError(
+          'Can only specify one of alignCenter, alignTop, alignBottom');
+    }
+    var scrollIntoViewIfNeeded = false;
+$if DART2JS
+    scrollIntoViewIfNeeded = JS('bool', '!!(#.scrollIntoViewIfNeeded)', this);
+$endif
+    if (alignTop != null) {
+      this.$dom_scrollIntoView(alignTop);
+    } else if (alignBottom != null) {
+      this.$dom_scrollIntoView(alignBottom);
+    } else if (scrollIntoViewIfNeeded) {
+      if (alignCenter != null) {
+        this.$dom_scrollIntoViewIfNeeded(alignCenter);
+      } else {
+        this.$dom_scrollIntoViewIfNeeded();
+      }
+    } else {
+      this.$dom_scrollIntoView();
+    }
+  }
+
 $if DART2JS
   @DomName('Element.mouseWheelEvent')
   static const EventStreamProvider<WheelEvent> mouseWheelEvent =
       const _CustomEventStreamProvider<WheelEvent>(
         Element._determineMouseWheelEventType);
 
   static String _determineMouseWheelEventType(EventTarget e) {
     if (JS('bool', '#.onwheel !== undefined', e)) {
       // W3C spec, and should be IE9+, but IE has a bug exposing onwheel.
       return 'wheel';
@@ skipping 269 matching lines @@
   // Optimization to improve performance until the dart2js compiler inlines this
   // method.
   static dynamic createElement_tag(String tag) =>
       // Firefox may return a JS function for some types (Embed, Object).
       JS('Element|=Object', 'document.createElement(#)', tag);
 $else
   static Element createElement_tag(String tag) =>
       document.$dom_createElement(tag);
 $endif
 }