Desktop Aura: Allow tab drags out of window.

ui/aura/root_window_host_linux.h

Index: ui/aura/root_window_host_linux.h
diff --git a/ui/aura/root_window_host_linux.h b/ui/aura/root_window_host_linux.h
index 94b6781b68737927bf635eb4d7436fc9a27bfa14..8e91c4d45915010cafa0b9fb1bbf3a53b2eec9ac 100644
--- a/ui/aura/root_window_host_linux.h
+++ b/ui/aura/root_window_host_linux.h
@@ -37,6 +37,7 @@ class RootWindowHostLinux : public RootWindowHost,
   virtual RootWindow* GetRootWindow() OVERRIDE;
   virtual gfx::AcceleratedWidget GetAcceleratedWidget() OVERRIDE;
   virtual void Show() OVERRIDE;
+  virtual void Hide() OVERRIDE;
   virtual void ToggleFullScreen() OVERRIDE;
   virtual gfx::Rect GetBounds() const OVERRIDE;
   virtual void SetBounds(const gfx::Rect& bounds) OVERRIDE;
@@ -77,6 +78,9 @@ class RootWindowHostLinux : public RootWindowHost,
   // Current Aura cursor.
   gfx::NativeCursor current_cursor_;
 
+  // Is the window mapped to the screen?
+  bool window_mapped_;
+
   // Is the cursor currently shown?
   bool cursor_shown_;