Introduce ash mojo interface for lock screen action handlers

ash/BUILD.gn

Index: ash/BUILD.gn
diff --git a/ash/BUILD.gn b/ash/BUILD.gn
index 675288182fff31e6ff03a503d30de07b992986ad..d44dc185362aae03551f50804ea2dc432c54bebe 100644
--- a/ash/BUILD.gn
+++ b/ash/BUILD.gn
@@ -44,6 +44,9 @@ component("ash") {
     "accelerators/spoken_feedback_toggler.h",
     "accessibility_delegate.h",
     "accessibility_types.h",
+    "action_handler/action_handler_state_controller.cc",
+    "action_handler/action_handler_state_controller.h",
+    "action_handler/action_handler_state_observer.h",
     "animation/animation_change_type.h",
     "app_list/app_list_delegate_impl.cc",
     "app_list/app_list_delegate_impl.h",
@@ -1137,6 +1140,7 @@ source_set("common_unittests") {
     "accelerators/accelerator_filter_unittest.cc",
     "accelerators/accelerator_table_unittest.cc",
     "accelerators/spoken_feedback_toggler_unittest.cc",
+    "action_handler/action_handler_state_controller_unittest.cc",
     "ash_touch_exploration_manager_chromeos_unittest.cc",
     "autoclick/autoclick_unittest.cc",
     "devtools/ash_devtools_unittest.cc",