Added tracking of memory usage within ApiNativeScopes. Usage to be displayed within Observatory.

runtime/vm/dart_api_state.cc

 // Copyright (c) 2016, 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.
 
 #include "vm/dart_api_state.h"
 
 #include "platform/assert.h"
 #include "platform/utils.h"
 #include "vm/heap.h"
 #include "vm/isolate.h"
 #include "vm/lockers.h"
 #include "vm/thread.h"
 #include "vm/timeline.h"
 
 namespace dart {
 
+intptr_t ApiNativeScope::current_memory_usage_ = 0;
+
 BackgroundFinalizer::BackgroundFinalizer(Isolate* isolate,
                                          FinalizationQueue* queue)
     : isolate_(isolate), queue_(queue) {
   ASSERT(FLAG_background_finalization);
   PageSpace* old_space = isolate->heap()->old_space();
   MonitorLocker ml(old_space->tasks_lock());
   old_space->set_tasks(old_space->tasks() + 1);
 }
 
 
@@ skipping 17 matching lines @@
 
   {
     PageSpace* old_space = isolate_->heap()->old_space();
     MonitorLocker ml(old_space->tasks_lock());
     old_space->set_tasks(old_space->tasks() - 1);
     ml.NotifyAll();
   }
 }
 
 }  // namespace dart