[Extensions Bindings] Add a bindings/ subdirectory under renderer

extensions/renderer/bindings/api_binding_js_util_unittest.cc

 // Copyright 2017 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.
 
-#include "extensions/renderer/api_binding_js_util.h"
+#include "extensions/renderer/bindings/api_binding_js_util.h"
 
 #include "base/bind.h"
-#include "extensions/renderer/api_binding_test_util.h"
-#include "extensions/renderer/api_bindings_system.h"
-#include "extensions/renderer/api_bindings_system_unittest.h"
+#include "extensions/renderer/bindings/api_binding_test_util.h"
+#include "extensions/renderer/bindings/api_bindings_system.h"
+#include "extensions/renderer/bindings/api_bindings_system_unittest.h"
 #include "gin/handle.h"
 
 namespace extensions {
 
 class APIBindingJSUtilUnittest : public APIBindingsSystemTest {
  protected:
   APIBindingJSUtilUnittest() {}
   ~APIBindingJSUtilUnittest() override {}
 
   gin::Handle<APIBindingJSUtil> CreateUtil() {
@@ skipping 163 matching lines @@
   EXPECT_EQ("alpha.functionWithCallback", last_request()->method_name);
   EXPECT_EQ("[\"stringy\"]", ValueToString(*last_request()->arguments));
   EXPECT_EQ(binding::RequestThread::UI, last_request()->thread);
   bindings_system()->CompleteRequest(last_request()->request_id,
                                      base::ListValue(), std::string());
   EXPECT_EQ("true", GetStringPropertyFromObject(context->Global(), context,
                                                 "callbackCalled"));
 }
 
 }  // namespace extensions