[ios Mojo] iOS facade class for Mojo API.

ios/web/BUILD.gn

Index: ios/web/BUILD.gn
diff --git a/ios/web/BUILD.gn b/ios/web/BUILD.gn
index 953e53713eaae0da318d8dc126a55062e23392b8..3a08cd6a946f2946f6099b639b7490d56d7905f4 100644
--- a/ios/web/BUILD.gn
+++ b/ios/web/BUILD.gn
@@ -14,7 +14,10 @@ source_set("web") {
     "//components/url_formatter",
     "//ios/net",
     "//ios/third_party/blink:html_tokenizer",
+    "//mojo/edk/system",
+    "//mojo/public/cpp/system",
     "//net",
+    "//services/shell/public/cpp",
     "//ui/base",
     "//ui/gfx",
     "//ui/gfx/geometry:geometry",
@@ -230,6 +233,8 @@ source_set("web") {
     "webui/crw_web_ui_manager.mm",
     "webui/crw_web_ui_page_builder.h",
     "webui/crw_web_ui_page_builder.mm",
+    "webui/mojo_facade.h",
+    "webui/mojo_facade.mm",
     "webui/shared_resources_data_source_ios.h",
     "webui/shared_resources_data_source_ios.mm",
     "webui/url_data_manager_ios.cc",
@@ -284,6 +289,7 @@ source_set("test_support") {
     "//base/test:test_support",
     "//ios/testing:ocmock_support",
     "//ios/third_party/gcdwebserver",
+    "//ios/web/test:mojo_bindings",
     "//net:test_support",
     "//testing/gmock",
     "//testing/gtest",
@@ -426,6 +432,7 @@ test("ios_web_unittests") {
     "web_state/wk_web_view_security_util_unittest.mm",
     "webui/crw_web_ui_manager_unittest.mm",
     "webui/crw_web_ui_page_builder_unittest.mm",
+    "webui/mojo_facade_unittest.mm",
     "webui/url_fetcher_block_adapter_unittest.mm",
   ]
 }