Eliminate WindowTreeConnection

mash/wm/user_window_controller_impl.cc

Index: mash/wm/user_window_controller_impl.cc
diff --git a/mash/wm/user_window_controller_impl.cc b/mash/wm/user_window_controller_impl.cc
index de983c7c325de710937992044c3fcca234b080de..7e87f01d8acd0e36c6f88b9a09ddb18355330617 100644
--- a/mash/wm/user_window_controller_impl.cc
+++ b/mash/wm/user_window_controller_impl.cc
@@ -7,7 +7,7 @@
 #include "components/mus/public/cpp/property_type_converters.h"
 #include "components/mus/public/cpp/window.h"
 #include "components/mus/public/cpp/window_property.h"
-#include "components/mus/public/cpp/window_tree_connection.h"
+#include "components/mus/public/cpp/window_tree_client.h"
 #include "mash/wm/property_util.h"
 #include "mash/wm/public/interfaces/container.mojom.h"
 #include "mash/wm/root_window_controller.h"
@@ -40,7 +40,7 @@ mojom::UserWindowPtr GetUserWindow(mus::Window* window) {
   user_window->window_app_icon = GetWindowAppIcon(window);
   user_window->window_app_id = mojo::String::From(GetAppID(window));
   user_window->ignored_by_shelf = GetWindowIgnoredByShelf(window);
-  mus::Window* focused = window->connection()->GetFocusedWindow();
+  mus::Window* focused = window->window_tree()->GetFocusedWindow();
   focused = GetTopLevelWindow(focused, window->parent());
   user_window->window_has_focus = focused == window;
   return user_window;
@@ -102,7 +102,7 @@ void UserWindowControllerImpl::Initialize(
   DCHECK(!root_controller_);
   root_controller_ = root_controller;
   GetUserWindowContainer()->AddObserver(this);
-  GetUserWindowContainer()->connection()->AddObserver(this);
+  GetUserWindowContainer()->window_tree()->AddObserver(this);
   window_property_observer_.reset(new WindowPropertyObserver(this));
   for (mus::Window* window : GetUserWindowContainer()->children()) {
     AssignIdIfNecessary(window);
@@ -117,7 +117,7 @@ void UserWindowControllerImpl::AssignIdIfNecessary(mus::Window* window) {
 
 void UserWindowControllerImpl::RemoveObservers(mus::Window* user_container) {
   user_container->RemoveObserver(this);
-  user_container->connection()->RemoveObserver(this);
+  user_container->window_tree()->RemoveObserver(this);
   for (auto iter : user_container->children())
     iter->RemoveObserver(window_property_observer_.get());
 }