Fixes three crashes

athena/home/home_card_impl.cc

 // Copyright 2014 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 "athena/home/public/home_card.h"
 
 #include <cmath>
 #include <limits>
 
 #include "athena/common/container_priorities.h"
@@ skipping 468 matching lines @@
   instance = this;
   WindowManager::GetInstance()->AddObserver(this);
 }
 
 HomeCardImpl::~HomeCardImpl() {
   DCHECK(instance);
   WindowManager::GetInstance()->RemoveObserver(this);
   if (activation_client_)
     activation_client_->RemoveObserver(this);
   home_card_widget_->CloseNow();
+
+  // Reset the view delegate first as it access search provider during
+  // shutdown.
+  view_delegate_.reset();
+  search_provider_.reset();
   instance = NULL;
 }
 
 void HomeCardImpl::Init() {
   InstallAccelerators();
   ScreenManager::ContainerParams params("HomeCardContainer", CP_HOME_CARD);
   params.can_activate_children = true;
   aura::Window* container = ScreenManager::Get()->CreateContainer(params);
   layout_manager_ = new HomeCardLayoutManager(this);
 
@@ skipping 160 matching lines @@
   instance = NULL;
 }
 
 // static
 HomeCard* HomeCard::Get() {
   DCHECK(instance);
   return instance;
 }
 
 }  // namespace athena