Remove unnecessary spin in ToolTipController

ui/wm/public/tooltip_client.h

Index: ui/wm/public/tooltip_client.h
diff --git a/ui/wm/public/tooltip_client.h b/ui/wm/public/tooltip_client.h
index 77095153b6e95ae6cb72558a3c4538718654d63d..2b0ebcf38b48bbce7e136acbf56bb5b20b6e483e 100644
--- a/ui/wm/public/tooltip_client.h
+++ b/ui/wm/public/tooltip_client.h
@@ -6,6 +6,7 @@
 #define UI_WM_PUBLIC_TOOLTIP_CLIENT_H_
 
 #include "ui/aura/aura_export.h"
+#include "ui/aura/window.h"
 #include "ui/gfx/font.h"
 
 namespace gfx {
@@ -52,6 +53,10 @@ AURA_EXPORT void SetTooltipId(Window* window, void* id);
 AURA_EXPORT const base::string16 GetTooltipText(Window* window);
 AURA_EXPORT const void* GetTooltipId(Window* window);
 
+AURA_EXPORT extern const aura::WindowProperty<void*>* const kTooltipIdKey;
+AURA_EXPORT extern const aura::WindowProperty<base::string16*>* const
+    kTooltipTextKey;
+
 }  // namespace client
 }  // namespace aura