[observatory] Add a 'GC' button to heap map.

runtime/observatory/lib/src/elements/heap_map.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.
 
 library heap_map_element;
 
 import 'dart:async';
 import 'dart:html';
 import 'dart:math';
 import 'package:observatory/models.dart' as M;
@@ skipping 90 matching lines @@
 
     // Set hover text to describe the object under the cursor.
     _canvas.title = _status;
 
     children = [
       navBar([
         new NavTopMenuElement(queue: _r.queue),
         new NavVMMenuElement(_vm, _events, queue: _r.queue),
         new NavIsolateMenuElement(_isolate, _events, queue: _r.queue),
         navMenu('heap map'),
+        new NavRefreshElement(label: 'GC', queue: _r.queue)
+          ..onRefresh.listen((_) => _refresh(gc: true)),
         new NavRefreshElement(queue: _r.queue)
           ..onRefresh.listen((_) => _refresh()),
         new NavNotifyElement(_notifications, queue: _r.queue)
       ]),
       new DivElement()
         ..classes = ['content-centered-big']
         ..children = [
           new HeadingElement.h2()..text = _status,
           new HRElement(),
         ],
@@ skipping 149 matching lines @@
       pixel = pixel.next();
     }
     _canvas.context2D.putImageData(
         _fragmentationData, 0, 0, 0, startY, _fragmentationData.width, endY);
     // Continue with the next page, asynchronously.
     new Future(() {
       _renderPages(startPage + 1);
     });
   }
 
-  Future _refresh() {
+  Future _refresh({gc: false}) {
     final isolate = _isolate as S.Isolate;
-    return isolate.invokeRpc('_getHeapMap', {}).then((S.ServiceMap response) {
+    var params = {};
+    if (gc) {
+      params['gc'] = 'full';
+    }
+    return isolate
+        .invokeRpc('_getHeapMap', params)
+        .then((S.ServiceMap response) {
       assert(response['type'] == 'HeapMap');
       _fragmentation = response;
       _updateFragmentationData();
     });
   }
 }
 
 // A reference to a particular pixel of ImageData.
 class PixelReference {
   final _data;
@@ skipping 21 matching lines @@
 
   // The row-major index of this pixel.
   int get index => _dataIndex ~/ NUM_COLOR_COMPONENTS;
 }
 
 class ObjectInfo {
   final address;
   final size;
   ObjectInfo(this.address, this.size);
 }