Overscan calibration UI.

ash/display/display_controller.h

Index: ash/display/display_controller.h
diff --git a/ash/display/display_controller.h b/ash/display/display_controller.h
index 38cff6d9769a8cfef55cc139642810494bfe22a0..2a42ab0e0ccf4c9f61542f2a94e72edf9f010466 100644
--- a/ash/display/display_controller.h
+++ b/ash/display/display_controller.h
@@ -125,6 +125,10 @@ class ASH_EXPORT DisplayController : public aura::DisplayObserver {
   // mode, this return a RootWindowController for the primary root window only.
   std::vector<internal::RootWindowController*> GetAllRootWindowControllers();
 
+  // Returns the current overscan insets for the specified |display_id|. See
+  // multi_display_manager.h for the details.
+  gfx::Insets GetOverscanInsets(int64 display_id);
+
   const DisplayLayout& default_display_layout() const {
     return default_display_layout_;
   }