[ios] Adds a CommandDispatcher to proxy method calls to UI handlers.

ios/clean/chrome/browser/ui/commands/BUILD.gn

Index: ios/clean/chrome/browser/ui/commands/BUILD.gn
diff --git a/ios/clean/chrome/browser/ui/commands/BUILD.gn b/ios/clean/chrome/browser/ui/commands/BUILD.gn
index 8b12cb4a8a72c0ac921a78943b8e48a5a3f2b7a9..6ad215da5c1f54ebd6bc1230c69255812dddce46 100644
--- a/ios/clean/chrome/browser/ui/commands/BUILD.gn
+++ b/ios/clean/chrome/browser/ui/commands/BUILD.gn
@@ -4,11 +4,30 @@
 
 source_set("commands") {
   sources = [
+    "command_dispatcher.h",
+    "command_dispatcher.mm",
     "settings_commands.h",
     "tab_commands.h",
     "tab_grid_commands.h",
     "toolbar_commands.h",
   ]
+  deps = [
+    "//base",
+  ]
+
+  configs += [ "//build/config/compiler:enable_arc" ]
+}
+
+source_set("unit_tests") {
+  testonly = true
+  sources = [
+    "command_dispatcher_unittest.mm",
+  ]
+  deps = [
+    ":commands",
+    "//base",
+    "//testing/gtest",
+  ]
 
   configs += [ "//build/config/compiler:enable_arc" ]
 }