Fix memory leak in CPU Profile page

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.
   static const subtreeIndent = 2;
 
   TableTreeRow(this.tree, TableTreeRow parent) :
       parent = parent,
       depth = parent != null ? parent.depth + 1 : 0 {
   }
 
   final TableTree tree;
   final TableTreeRow parent;
   final int depth;
   final List<TableTreeRow> children = new List<TableTreeRow>();
   final List<TableCellElement> _tableColumns = new List<TableCellElement>();
   final List<DivElement> flexColumns = new List<DivElement>();
+  final List<StreamSubscription> listeners = new List<StreamSubscription>();
+
   SpanElement _expander;
   TableRowElement _tr;
   TableRowElement get tr => _tr;
   bool _expanded = false;
   bool get expanded => _expanded;
   set expanded(bool expanded) {
     var changed = _expanded != expanded;
     _expanded = expanded;
     if (changed) {
       // If the state has changed, fire callbacks.
@@ skipping 26 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 = '1.5em';
-    expander.onClick.listen(onClick);
+    listeners.add(expander.onClick.listen(onClick));
     return expander;
   }
 
+  void _cleanUpListeners() {
+    for (var i = 0; i < listeners.length; i++) {
+      listeners[i].cancel();
+    }
+    listeners.clear();
+  }
+
   void onClick(Event e) {
     e.stopPropagation();
     tree.toggle(this);
   }
 
   static const redColor = '#F44336';
   static const blueColor = '#3F51B5';
   static const purpleColor = '#673AB7';
   static const greenColor = '#4CAF50';
   static const orangeColor = '#FF9800';
@@ skipping 21 matching lines @@
     var backgroundColor = lightGrayColor;
     if (depth > 1) {
       var colorIndex = (depth - 1) % backgroundColors.length;
       backgroundColor = backgroundColors[colorIndex];
     }
     var colorBlock = _makeColorBlock(backgroundColor);
     firstColumn.children.add(colorBlock);
     _expander = _makeExpander();
     firstColumn.children.add(_expander);
     // Enable expansion by clicking anywhere on the first column.
-    firstColumn.onClick.listen(onClick);
+    listeners.add(firstColumn.onClick.listen(onClick));
     _updateExpanderView();
   }
 
   void _updateExpanderView() {
     if (_expander == null) {
       return;
     }
     if (!hasChildren()) {
       _expander.style.visibility = 'hidden';
       _expander.classes.remove('pointer');
@@ skipping 20 matching lines @@
   /// Fired when the tree row is being hidden.
   void onHide() {
     _tr = null;
     _expander = null;
     if (_tableColumns != null) {
       _tableColumns.clear();
     }
     if (flexColumns != null) {
       flexColumns.clear();
     }
+    _cleanUpListeners();
   }
 }
 
 class TableTree extends Observable {
   final TableSectionElement tableBody;
   final List<TableTreeRow> rows = [];
   final int columnCount;
   Future _pendingOperation;
   /// Create a table tree with column [headers].
   TableTree(this.tableBody, this.columnCount);
 
   void clear() {
     tableBody.children.clear();
+    for (var i = 0; i < rows.length; i++) {
+      rows[i]._cleanUpListeners();
+    }
     rows.clear();
   }
 
   /// Initialize the table tree with the list of root children.
   void initialize(TableTreeRow root) {
     clear();
     root.onShow();
     toggle(root);
   }
 
@@ skipping 170 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];
   }
 }