Clamp dialog bounds to be fully visible on the nearest display

ui/display/screen.h

Index: ui/display/screen.h
diff --git a/ui/display/screen.h b/ui/display/screen.h
index 3e1b0a0f13de434872dad1f469cd2831aac1a33d..3cfc9d4187b9e32e9da7632a17fe6ca10bb59788 100644
--- a/ui/display/screen.h
+++ b/ui/display/screen.h
@@ -38,6 +38,12 @@ class DISPLAY_EXPORT Screen {
   // Tests must be sure to reset any state they install.
   static void SetScreenInstance(Screen* instance);
 
+  // If the given |screen_rect| isn't fully on any display, return a rect that
+  // is fully within the bounds of the work area for the nearest display. If
+  // the rect is already fully on a display, no changes are made.
+  static gfx::Rect MoveScreenRectToNearestDisplay(
+      const gfx::Rect& screen_rect);
+
   // Returns the current absolute position of the mouse pointer.
   virtual gfx::Point GetCursorScreenPoint() = 0;