Remove DisplayChangeObserver ash dependencies.

ash/display/window_tree_host_manager.cc

Index: ash/display/window_tree_host_manager.cc
diff --git a/ash/display/window_tree_host_manager.cc b/ash/display/window_tree_host_manager.cc
index 2182595732a45b10d59dd989c0e9533794dd5574..73a1707538d6eb2e4f86de4ea9e0b9af32f5166d 100644
--- a/ash/display/window_tree_host_manager.cc
+++ b/ash/display/window_tree_host_manager.cc
@@ -29,7 +29,6 @@
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/thread_task_runner_handle.h"
-#include "grit/ash_strings.h"
 #include "ui/aura/client/capture_client.h"
 #include "ui/aura/client/focus_client.h"
 #include "ui/aura/client/screen_position_client.h"
@@ -840,14 +839,6 @@ ui::DisplayConfigurator* WindowTreeHostManager::display_configurator() {
 }
 #endif
 
-std::string WindowTreeHostManager::GetInternalDisplayNameString() {
-  return l10n_util::GetStringUTF8(IDS_ASH_INTERNAL_DISPLAY_NAME);
-}
-
-std::string WindowTreeHostManager::GetUnknownDisplayNameString() {
-  return l10n_util::GetStringUTF8(IDS_ASH_STATUS_TRAY_UNKNOWN_DISPLAY_NAME);
-}
-
 ui::EventDispatchDetails WindowTreeHostManager::DispatchKeyEventPostIME(
     ui::KeyEvent* event) {
   // Getting the active root window to dispatch the event. This isn't