aura: Add X11 host window management.

ui/aura/root_window_observer.h

Index: ui/aura/root_window_observer.h
diff --git a/ui/aura/root_window_observer.h b/ui/aura/root_window_observer.h
index 9f4cfd9ba5e7a0b9c828eb9c5b753c14205679c1..2682bd2ce81b76066431ace18cc79a81165ef907 100644
--- a/ui/aura/root_window_observer.h
+++ b/ui/aura/root_window_observer.h
@@ -6,6 +6,7 @@
 #define UI_AURA_ROOT_WINDOW_OBSERVER_H_
 
 #include "ui/aura/aura_export.h"
+#include "ui/base/cursor/cursor.h"
 
 namespace gfx {
 class Size;
@@ -28,6 +29,10 @@ class AURA_EXPORT RootWindowObserver {
   // Invoked when the keyboard mapping has changed.
   virtual void OnKeyboardMappingChanged(const RootWindow* root) {}
 
+  // Invoked when the cursor has changed.
+  virtual void OnCursorChanged(
+      const RootWindow* root, ui::PlatformCursor cursor) {}
+
  protected:
   virtual ~RootWindowObserver() {}
 };