All together now

ash/display/display_controller.cc

 // Copyright (c) 2012 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 "ash/display/display_controller.h"
 
 #include <algorithm>
 #include <cmath>
 #include <map>
 
@@ skipping 679 matching lines @@
   internal::RootWindowController* controller =
       GetRootWindowController(root_to_delete);
   DCHECK(controller);
   controller->MoveWindowsTo(GetPrimaryRootWindow());
   // Delete most of root window related objects, but don't delete
   // root window itself yet because the stack may be using it.
   controller->Shutdown();
   base::MessageLoop::current()->DeleteSoon(FROM_HERE, controller);
 }
 
+ui::Compositor* DisplayController::GetCompositorForDisplay(
+    const gfx::Display& display) {
+  aura::RootWindow* root_window = GetRootWindowForDisplayId(display.id());
+  return root_window ? root_window->compositor() : NULL;
+}
+
 void DisplayController::OnRootWindowHostResized(const aura::RootWindow* root) {
   internal::DisplayManager* display_manager = GetDisplayManager();
   gfx::Display display = GetDisplayNearestWindow(root);
   if (display_manager->UpdateDisplayBounds(
           display.id(),
           gfx::Rect(root->GetHostOrigin(), root->GetHostSize()))) {
     mirror_window_controller_->UpdateWindow();
   }
 }
 
@@ skipping 115 matching lines @@
   for (size_t i = 0; i < root_windows.size(); ++i) {
     std::string name =
         root_windows[i] == primary ? "aura_root_0" : "aura_root_x";
     gfx::AcceleratedWidget xwindow = root_windows[i]->GetAcceleratedWidget();
     XStoreName(ui::GetXDisplay(), xwindow, name.c_str());
   }
 #endif
 }
 
 }  // namespace ash