Implements accessibility bridge in common library (#23491)

Author: chunhtai

ci/licenses_golden/licenses_flutter

@@ -870,6 +870,9 @@ FILE: ../../../flutter/shell/platform/android/surface/android_surface_mock.cc
 FILE: ../../../flutter/shell/platform/android/surface/android_surface_mock.h
 FILE: ../../../flutter/shell/platform/android/vsync_waiter_android.cc
 FILE: ../../../flutter/shell/platform/android/vsync_waiter_android.h
+FILE: ../../../flutter/shell/platform/common/cpp/accessibility_bridge.cc
+FILE: ../../../flutter/shell/platform/common/cpp/accessibility_bridge.h
+FILE: ../../../flutter/shell/platform/common/cpp/accessibility_bridge_unittests.cc
 FILE: ../../../flutter/shell/platform/common/cpp/client_wrapper/basic_message_channel_unittests.cc
 FILE: ../../../flutter/shell/platform/common/cpp/client_wrapper/binary_messenger_impl.h
 FILE: ../../../flutter/shell/platform/common/cpp/client_wrapper/byte_buffer_streams.h
@@ -911,6 +914,9 @@ FILE: ../../../flutter/shell/platform/common/cpp/client_wrapper/texture_registra
 FILE: ../../../flutter/shell/platform/common/cpp/engine_switches.cc
 FILE: ../../../flutter/shell/platform/common/cpp/engine_switches.h
 FILE: ../../../flutter/shell/platform/common/cpp/engine_switches_unittests.cc
+FILE: ../../../flutter/shell/platform/common/cpp/flutter_platform_node_delegate.cc
+FILE: ../../../flutter/shell/platform/common/cpp/flutter_platform_node_delegate.h
+FILE: ../../../flutter/shell/platform/common/cpp/flutter_platform_node_delegate_unittests.cc
 FILE: ../../../flutter/shell/platform/common/cpp/incoming_message_dispatcher.cc
 FILE: ../../../flutter/shell/platform/common/cpp/incoming_message_dispatcher.h
 FILE: ../../../flutter/shell/platform/common/cpp/json_message_codec.cc
@@ -926,6 +932,8 @@ FILE: ../../../flutter/shell/platform/common/cpp/public/flutter_export.h
 FILE: ../../../flutter/shell/platform/common/cpp/public/flutter_messenger.h
 FILE: ../../../flutter/shell/platform/common/cpp/public/flutter_plugin_registrar.h
 FILE: ../../../flutter/shell/platform/common/cpp/public/flutter_texture_registrar.h
+FILE: ../../../flutter/shell/platform/common/cpp/test_accessibility_bridge.cc
+FILE: ../../../flutter/shell/platform/common/cpp/test_accessibility_bridge.h
 FILE: ../../../flutter/shell/platform/common/cpp/text_input_model.cc
 FILE: ../../../flutter/shell/platform/common/cpp/text_input_model.h
 FILE: ../../../flutter/shell/platform/common/cpp/text_input_model_unittests.cc

shell/platform/common/cpp/BUILD.gn

@@ -68,6 +68,26 @@ source_set("common_cpp_switches") {
   ]
 }
 
+source_set("common_cpp_accessibility") {
+  public = [
+    "accessibility_bridge.h",
+    "flutter_platform_node_delegate.h",
+  ]
+
+  sources = [
+    "accessibility_bridge.cc",
+    "flutter_platform_node_delegate.cc",
+  ]
+
+  public_configs =
+      [ "//flutter/third_party/accessibility:accessibility_config" ]
+
+  public_deps = [
+    "//flutter/shell/platform/embedder:embedder_as_internal_library",
+    "//flutter/third_party/accessibility",
+  ]
+}
+
 source_set("common_cpp") {
   public = [
     "incoming_message_dispatcher.h",
@@ -156,6 +176,18 @@ if (enable_unittests) {
       "//flutter/testing",
     ]
 
+    # The accessibility bridge only supports MacOS for now.
+    if (is_mac) {
+      sources += [
+        "accessibility_bridge_unittests.cc",
+        "flutter_platform_node_delegate_unittests.cc",
+        "test_accessibility_bridge.cc",
+        "test_accessibility_bridge.h",
+      ]
+
+      deps += [ ":common_cpp_accessibility" ]
+    }
+
     public_configs = [ "//flutter:config" ]
   }
 }