* Electron version: 1.6.7
* Operating system: Mac OS X 10.10.5 and Windows 8.1

I realize 1.6.7 is still in beta but thought I should report a memory leak I am seeing...  in a simple app that does window.open with every new window opened the memory keeps growing and is never released when the sub-windows get closed.

The demo repo is committed here: https://github.com/lneir/electron-memory-leak

To repo.
1. git clone https://github.com/lneir/electron-memory-leak.git
2. npm i
3. npm run start
4. in the main window click the open window button 5 times.
Notice: the memory goes very high (approx 500 Mbytes) because each sub-window is allocating a big chunk of memory.
5. now close all the open windows.

Result: the memory of the renderer process stays very high
Expected: memory to go back to original before all sub-windows were opened.

Note: This does not happen on electron 1.4.16 but only appears to be a problem in electron 1.6.7.  
Note: Also the problem seems to be related to the having preload enabled

atom/common/api/object_life_monitor.cc
v8::Local<v8::Object> target)
    : context_(isolate, isolate->GetCurrentContext()),
      target_(isolate, target),
      weak_ptr_factory_(this) {
  target_.SetWeak(this, OnObjectGC, v8::WeakCallbackType::kParameter);
}
ObjectLifeMonitor::~ObjectLifeMonitor() {
  if (target_.IsEmpty())
    return;
  target_.ClearWeak();
  target_.Reset();
}
void ObjectLifeMonitor::OnObjectGC(
    const v8::WeakCallbackInfo<ObjectLifeMonitor>& data) {
  ObjectLifeMonitor* self = data.GetParameter();
  self->target_.Reset();
  self->RunDestructor();
  data.SetSecondPassCallback(Free);
}
void ObjectLifeMonitor::Free(
    const v8::WeakCallbackInfo<ObjectLifeMonitor>& data) {
  delete data.GetParameter();
}
}