Improve class-tree, class-view, and instance-view.

runtime/observatory/lib/src/app/view_model.dart

 // Copyright (c) 2014, 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 app;
 
 abstract class TableTreeRow extends Observable {
   static const arrowRight = '\u2192';
   static const arrowDownRight = '\u21b3';
   // Number of ems each subtree is indented.
@@ skipping 50 matching lines @@
 
   HtmlElement _makeColorBlock(String backgroundColor) {
     var colorBlock = new DivElement();
     colorBlock.style.minWidth = '2px';
     colorBlock.style.backgroundColor = backgroundColor;
     return colorBlock;
   }
 
   HtmlElement _makeExpander() {
     var expander = new SpanElement();
-    expander.style.minWidth = '2em';
+    expander.style.minWidth = '24px';
+    expander.style.minHeight = '24px';
     listeners.add(expander.onClick.listen(onClick));
     return expander;
   }
 
   void _cleanUpListeners() {
     for (var i = 0; i < listeners.length; i++) {
       listeners[i].cancel();
     }
     listeners.clear();
   }
@@ skipping 280 matching lines @@
     if (column != _sortColumnIndex) {
       return columns[column].label + '\u2003';
     }
     return columns[column].label + (_sortDescending ? arrowUp : arrowDown);
   }
 
   dynamic getValue(int row, int column) {
     return rows[row].values[column];
   }
 }