Fix crashers and issues when rendering blimp in tabs

blimp/client/core/contents/blimp_navigation_controller_impl.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "blimp/client/core/contents/blimp_navigation_controller_impl.h"
 
 #include "blimp/client/core/contents/blimp_navigation_controller_delegate.h"
 
 namespace {
 // TODO(shaktisahu): NavigationFeature currently needs a tab_id. Remove this
 // later when it is fully integrated with BlimpClientContext.
 const int kDummyTabId = 0;
 }  // namespace
 
 namespace blimp {
 namespace client {
 
 BlimpNavigationControllerImpl::BlimpNavigationControllerImpl(
     BlimpNavigationControllerDelegate* delegate,
     NavigationFeature* feature)
     : navigation_feature_(feature), delegate_(delegate) {
   if (navigation_feature_)
     navigation_feature_->SetDelegate(kDummyTabId, this);
 }
 
-BlimpNavigationControllerImpl::~BlimpNavigationControllerImpl() = default;
+BlimpNavigationControllerImpl::~BlimpNavigationControllerImpl() {
+  if (navigation_feature_)
+    navigation_feature_->RemoveDelegate(kDummyTabId);
+}
 
 void BlimpNavigationControllerImpl::LoadURL(const GURL& url) {
   current_url_ = url;
   navigation_feature_->NavigateToUrlText(kDummyTabId, current_url_.spec());
 }
 
 void BlimpNavigationControllerImpl::Reload() {
   navigation_feature_->Reload(kDummyTabId);
 }
 
@@ skipping 44 matching lines @@
   delegate_->OnLoadingStateChanged(loading);
 }
 
 void BlimpNavigationControllerImpl::OnPageLoadStatusUpdate(int tab_id,
                                                            bool completed) {
   delegate_->OnNavigationStateChanged();
 }
 
 }  // namespace client
 }  // namespace blimp