[Extensions Bindings] Add a bindings/ subdirectory under renderer

extensions/renderer/bindings/api_last_error_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_last_error.h"
+#include "extensions/renderer/bindings/api_last_error.h"
 
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/optional.h"
-#include "extensions/renderer/api_binding_test.h"
-#include "extensions/renderer/api_binding_test_util.h"
+#include "extensions/renderer/bindings/api_binding_test.h"
+#include "extensions/renderer/bindings/api_binding_test_util.h"
 #include "gin/converter.h"
 #include "gin/public/context_holder.h"
 
 namespace extensions {
 
 namespace {
 
 void DoNothingWithError(v8::Local<v8::Context> context,
                         const std::string& error) {}
 
@@ skipping 194 matching lines @@
   last_error.ClearError(context_b, false);
   EXPECT_EQ("\"Last error a\"", GetLastErrorMessage(parent_a, context_a));
   EXPECT_EQ("undefined", GetLastErrorMessage(parent_b, context_b));
 
   last_error.ClearError(context_a, false);
   EXPECT_EQ("undefined", GetLastErrorMessage(parent_a, context_a));
   EXPECT_EQ("undefined", GetLastErrorMessage(parent_b, context_b));
 }
 
 }  // namespace extensions