Revert of [Athena, Cleanup] rename WidnowManager::GetInstance -> ::Get

athena/resource_manager/resource_manager_impl.cc

Index: athena/resource_manager/resource_manager_impl.cc
diff --git a/athena/resource_manager/resource_manager_impl.cc b/athena/resource_manager/resource_manager_impl.cc
index 9c18a757a4611e925db5309504e7a58e31dd9d71..8e10cb8b8b3fbc8015d5763bb9bf6d6dcf2949ea 100644
--- a/athena/resource_manager/resource_manager_impl.cc
+++ b/athena/resource_manager/resource_manager_impl.cc
@@ -167,15 +167,15 @@
       next_resource_management_time_(base::Time::Now()),
       wait_time_for_resource_deallocation_(base::TimeDelta::FromMilliseconds(
           delegate_->MemoryPressureIntervalInMS())) {
-  WindowManager::Get()->AddObserver(this);
-  WindowManager::Get()->GetWindowListProvider()->AddObserver(this);
+  WindowManager::GetInstance()->AddObserver(this);
+  WindowManager::GetInstance()->GetWindowListProvider()->AddObserver(this);
   ActivityManager::Get()->AddObserver(this);
 }
 
 ResourceManagerImpl::~ResourceManagerImpl() {
   ActivityManager::Get()->RemoveObserver(this);
-  WindowManager::Get()->GetWindowListProvider()->RemoveObserver(this);
-  WindowManager::Get()->RemoveObserver(this);
+  WindowManager::GetInstance()->GetWindowListProvider()->RemoveObserver(this);
+  WindowManager::GetInstance()->RemoveObserver(this);
 
   while (!activity_list_.empty())
     OnActivityEnding(activity_list_.front());
@@ -418,7 +418,7 @@
     return;
   std::vector<Activity*> new_activity_list;
   const aura::Window::Windows children =
-      WindowManager::Get()->GetWindowListProvider()->GetWindowList();
+      activity_list_[0]->GetWindow()->parent()->children();
   // Find the first window in the container which is part of the application.
   for (aura::Window::Windows::const_reverse_iterator child_iterator =
          children.rbegin();