[ozone/wayland] Implement basic keyboard handling support

ui/events/ozone/layout/xkb/xkb_keyboard_layout_engine.h

Index: ui/events/ozone/layout/xkb/xkb_keyboard_layout_engine.h
diff --git a/ui/events/ozone/layout/xkb/xkb_keyboard_layout_engine.h b/ui/events/ozone/layout/xkb/xkb_keyboard_layout_engine.h
index a338c18da655f44148c2f4ded001145a90fc87f6..aa24f5ba8b944921e5b325d2ca60c7d298e2ca60 100644
--- a/ui/events/ozone/layout/xkb/xkb_keyboard_layout_engine.h
+++ b/ui/events/ozone/layout/xkb/xkb_keyboard_layout_engine.h
@@ -50,6 +50,14 @@ class EVENTS_OZONE_LAYOUT_EXPORT XkbKeyboardLayoutEngine
                               std::string* layout_id,
                               std::string* layout_variant);
 
+  // Used to sync up client side 'xkb_state' instance with modifiers status
+  // update
+  // from the server.
+  int UpdateModifiers(uint32_t depressed_mods,
+                      uint32_t latched_mods,
+                      uint32_t locked_mods,
+                      uint32_t group);
+
  protected:
   // Table for EventFlagsToXkbFlags().
   struct XkbFlagMapEntry {
@@ -114,6 +122,12 @@ class EVENTS_OZONE_LAYOUT_EXPORT XkbKeyboardLayoutEngine
 
   std::string current_layout_name_;
 
+  struct {
+    xkb_mod_index_t control = 0;
+    xkb_mod_index_t alt = 0;
+    xkb_mod_index_t shift = 0;
+  } xkb_mod_indexes_;
+
   // Support weak pointers for attach & detach callbacks.
   base::WeakPtrFactory<XkbKeyboardLayoutEngine> weak_ptr_factory_;
 };