[mojo] Add typemap and variant support to generators

mojo/public/interfaces/bindings/tests/BUILD.gn

 # 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.
 
 import("../../../tools/bindings/mojom.gni")
 
 mojom("test_interfaces") {
   testonly = true
   sources = [
     "math_calculator.mojom",
@@ skipping 50 matching lines @@
 
 mojom("versioning_test_client_interfaces") {
   # FIXME: Dart packaged applications cannot depend on testonly mojoms.
   # testonly = true
   sources = [
     "versioning_test_client.mojom",
   ]
 
   with_environment = false
 }
+
+mojom("test_interfaces_chromium") {
+  testonly = true
+
+  sources = [
+    "test_native_types.mojom",
+  ]
+
+  variant = "chromium"
+  typemaps = [ "chromium_test.typemap" ]
+
+  with_environment = false
+
+  public_deps = [
+    ":test_interfaces",
+  ]
+}
+
+mojom("test_interfaces_blink") {
+  testonly = true
+
+  sources = [
+    "test_native_types.mojom",
+  ]
+
+  variant = "blink"
+  typemaps = [ "blink_test.typemap" ]
+
+  with_environment = false
+
+  public_deps = [
+    ":test_interfaces",
+  ]
+}