Fixed missing method referenced when MallocHooks is unsupported.

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

Index: runtime/observatory/lib/src/app/page.dart
diff --git a/runtime/observatory/lib/src/app/page.dart b/runtime/observatory/lib/src/app/page.dart
index aaee452b135d35eb50b06d9c747b37b4c3060e33..ddbec83872f6d3baec7ea3a0ca6b4cd5ccbc8ad3 100644
--- a/runtime/observatory/lib/src/app/page.dart
+++ b/runtime/observatory/lib/src/app/page.dart
@@ -21,6 +21,8 @@ final _isolateSampleProfileRepository = new IsolateSampleProfileRepository();
 final _libraryRepository = new LibraryRepository();
 final _megamorphicCacheRepository = new MegamorphicCacheRepository();
 final _metricRepository = new MetricRepository();
+final _nativeMemorySampleProfileRepository =
+    new NativeMemorySampleProfileRepository();
 final _objectPoolRepository = new ObjectPoolRepository();
 final _objectRepository = new ObjectRepository();
 final _objectstoreRepository = new ObjectStoreRepository();
@@ -190,6 +192,24 @@ class FlagsPage extends SimplePage {
   }
 }
 
+class NativeMemoryProfilerPage extends SimplePage {
+  NativeMemoryProfilerPage(app)
+      : super('native-memory-profile', 'native-memory-profile', app);
+  @override
+  onInstall() {
+    if (element == null) {
+      element = new NativeMemoryProfileElement(app.vm, app.events,
+          app.notifications, _nativeMemorySampleProfileRepository,
+          queue: app.queue);
+    }
+    assert(element != null);
+  }
+
+  void _visit(Uri uri) {
+    super._visit(uri);
+  }
+}
+
 class InspectPage extends MatchingPage {
   InspectPage(app) : super('inspect', app);