Remove DisplayChangeObserver ash dependencies.

ui/display/manager/display_manager.h

Index: ui/display/manager/display_manager.h
diff --git a/ui/display/manager/display_manager.h b/ui/display/manager/display_manager.h
index 2e1e90480f891a96a206d85f5fa35d43839c397f..42bc0eda3feef66714fc9663d5cd76babc3059da 100644
--- a/ui/display/manager/display_manager.h
+++ b/ui/display/manager/display_manager.h
@@ -22,6 +22,7 @@
 #include "ui/display/display_export.h"
 #include "ui/display/display_observer.h"
 #include "ui/display/manager/display_layout.h"
+#include "ui/display/manager/display_string_provider.h"
 #include "ui/display/manager/managed_display_info.h"
 #include "ui/display/types/display_constants.h"
 
@@ -74,9 +75,6 @@ class DISPLAY_EXPORT DisplayManager
     // Get the ui::DisplayConfigurator.
     virtual ui::DisplayConfigurator* display_configurator() = 0;
 #endif
-
-    virtual std::string GetInternalDisplayNameString() = 0;
-    virtual std::string GetUnknownDisplayNameString() = 0;
   };
 
   // How the second display will be used.
@@ -93,7 +91,8 @@ class DISPLAY_EXPORT DisplayManager
   // The display ID for a virtual display assigned to a unified desktop.
   static int64_t kUnifiedDisplayId;
 
-  explicit DisplayManager(std::unique_ptr<Screen> screen);
+  DisplayManager(std::unique_ptr<Screen> screen,
+                 std::unique_ptr<DisplayStringProvider> string_provider);
 #if defined(OS_CHROMEOS)
   ~DisplayManager() override;
 #else
@@ -408,7 +407,7 @@ class DISPLAY_EXPORT DisplayManager
   Delegate* delegate_ = nullptr;  // not owned.
 
   std::unique_ptr<Screen> screen_;
-
+  std::unique_ptr<DisplayStringProvider> string_provider_;
   std::unique_ptr<DisplayLayoutStore> layout_store_;
 
   int64_t first_display_id_ = kInvalidDisplayId;