Add DisplayPlacement/Layout mojoms + StructTraits.

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 dfb783fec6d91c8488087de75dc702ce3083c3f6..6fcde09353959087103b06413bd7f3d2de7acb71 100644
--- a/ui/display/display_layout.h
+++ b/ui/display/display_layout.h
@@ -69,6 +69,9 @@ struct DISPLAY_EXPORT DisplayPlacement {
 
   DisplayPlacement(const DisplayPlacement& placement);
 
+  bool operator==(const DisplayPlacement& other) const;
+  bool operator!=(const DisplayPlacement& other) const;
+
   DisplayPlacement& Swap();
 
   std::string ToString() const;