Detect and fix overlapping displays

ui/display/display_layout.h

Index: ui/display/display_layout.h
diff --git a/ui/display/display_layout.h b/ui/display/display_layout.h
index e9f85f75b95b2824f4c4e8f7f20f035a502b239d..0cec03dd79ba23d789b80ea4e2b6bfdd5a290bfa 100644
--- a/ui/display/display_layout.h
+++ b/ui/display/display_layout.h
@@ -86,10 +86,11 @@ class DISPLAY_EXPORT DisplayLayout final {
   // Applies the layout to the displays in |display_list|.
   // |updated_ids| (optional) contains the ids for displays whose bounds have
   // changed. |minimum_offset_overlap| represents the minimum required overlap
-  // between displays.
+  // between displays. Any overlap between displays will be fixed, and the
+  // display placement will be fixed.
   void ApplyToDisplayList(Displays* display_list,
                           std::vector<int64_t>* updated_ids,
-                          int minimum_offset_overlap) const;
+                          int minimum_offset_overlap);
 
   // Validates the layout object.
   static bool Validate(const DisplayIdList& list, const DisplayLayout& layout);
@@ -125,6 +126,10 @@ class DISPLAY_EXPORT DisplayLayout final {
                                     Displays* display_list,
                                     int minimum_offset_overlap);
 
+  // After this layout has been applied to the |display_list|, this function is
+  // called to update the offsets in the |placement_list|.
+  void UpdateOffsets(Displays* display_list);
+
   DISALLOW_COPY_AND_ASSIGN(DisplayLayout);
 };