Makes ash/wm/common a library

ash/wm/common/wm_display_observer.h

Index: ash/wm/common/wm_display_observer.h
diff --git a/ash/wm/common/wm_display_observer.h b/ash/wm/common/wm_display_observer.h
index 82bf5d8fe371407154c5359d87fbd582076bdda0..aaf9f0c601756e9c095cee6d4f91593487f9aed1 100644
--- a/ash/wm/common/wm_display_observer.h
+++ b/ash/wm/common/wm_display_observer.h
@@ -5,7 +5,7 @@
 #ifndef ASH_WM_COMMON_WM_DISPLAY_OBSERVER_H_
 #define ASH_WM_COMMON_WM_DISPLAY_OBSERVER_H_
 
-#include "ash/ash_export.h"
+#include "ash/wm/common/ash_wm_common_export.h"
 
 namespace ash {
 namespace wm {
@@ -13,7 +13,7 @@ namespace wm {
 class WmWindow;
 
 // Used to track changes in display configuration.
-class ASH_EXPORT WmDisplayObserver {
+class ASH_WM_COMMON_EXPORT WmDisplayObserver {
  public:
   virtual void OnDisplayConfigurationChanged() {}