Introdcue AshWindowTreeHost and move ash/chrome specific code in WTH to ash.

ash/accelerators/accelerator_controller.cc

Index: ash/accelerators/accelerator_controller.cc
diff --git a/ash/accelerators/accelerator_controller.cc b/ash/accelerators/accelerator_controller.cc
index 17b260e85bba4547bcf40e01532f97c0f52b2d6f..1d4455ae8014d51c67d982091714d8f3db574536 100644
--- a/ash/accelerators/accelerator_controller.cc
+++ b/ash/accelerators/accelerator_controller.cc
@@ -18,6 +18,7 @@
 #include "ash/display/display_manager.h"
 #include "ash/focus_cycler.h"
 #include "ash/gpu_support.h"
+#include "ash/host/ash_window_tree_host.h"
 #include "ash/ime_control_delegate.h"
 #include "ash/magnifier/magnification_controller.h"
 #include "ash/magnifier/partial_magnification_controller.h"
@@ -498,7 +499,7 @@ bool HandleToggleFullscreen(ui::KeyboardCode key_code) {
 }
 
 bool HandleToggleRootWindowFullScreen() {
-  Shell::GetPrimaryRootWindow()->GetHost()->ToggleFullScreen();
+  Shell::GetPrimaryRootWindowController()->ash_host()->ToggleFullScreen();
   return true;
 }
 
@@ -725,7 +726,7 @@ bool HandlePrintWindowHierarchy() {
   for (size_t i = 0; i < controllers.size(); ++i) {
     std::ostringstream out;
     out << "RootWindow " << i << ":\n";
-    PrintWindowHierarchy(controllers[i]->root_window(), 0, &out);
+    PrintWindowHierarchy(controllers[i]->GetRootWindow(), 0, &out);
     // Error so logs can be collected from end-users.
     LOG(ERROR) << out.str();
   }