[ozone/wayland] Implement basic keyboard handling support

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

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_EVENTS_OZONE_LAYOUT_XKB_XKB_KEYBOARD_LAYOUT_ENGINE_H_
 #define UI_EVENTS_OZONE_LAYOUT_XKB_XKB_KEYBOARD_LAYOUT_ENGINE_H_
 
 #include <stdint.h>
 #include <xkbcommon/xkbcommon.h>
 
@@ skipping 32 matching lines @@
 
   bool Lookup(DomCode dom_code,
               int flags,
               DomKey* dom_key,
               KeyboardCode* key_code) const override;
 
   static void ParseLayoutName(const std::string& layout_name,
                               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 {
     int ui_flag;
     xkb_mod_mask_t xkb_flag;
   };
   std::vector<XkbFlagMapEntry> xkb_flag_map_;
 
   // Flag mask for num lock, which is always considered enabled.
   xkb_mod_mask_t num_lock_mod_mask_ = 0;
@@ skipping 44 matching lines @@
   void OnKeymapLoaded(const std::string& layout_name,
                       std::unique_ptr<char, base::FreeDeleter> keymap_str);
 
   // libxkbcommon uses explicit reference counting for its structures,
   // so we need to trigger its cleanup.
   std::unique_ptr<xkb_context, XkbContextDeleter> xkb_context_;
   std::unique_ptr<xkb_state, XkbStateDeleter> xkb_state_;
 
   std::string current_layout_name_;
 
+  struct {
+    xkb_mod_index_t control;
+    xkb_mod_index_t alt;
+    xkb_mod_index_t shift;
+  } xkb_mod_indexes_{0, 0, 0};

[spang, 2017/01/24 20:41:50]

= {0, 0, 0};

Actually, probably even better to just do

struct {
  control = 0;
  alt = 0;
  shift = 0;
} xkb_mod_indexes_;

See
https://www.chromium.org/developers/coding-style/cpp-dos-and-donts#TOC-Variab...
for advice on which syntax to use for initializers.

[tonikitoo, 2017/01/24 21:51:10]

Done.

+
   // Support weak pointers for attach & detach callbacks.
   base::WeakPtrFactory<XkbKeyboardLayoutEngine> weak_ptr_factory_;
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_OZONE_LAYOUT_XKB_XKB_KEYBOARD_LAYOUT_ENGINE_H_