[Extensions Bindings] Introduce BindingAccessChecker

extensions/renderer/binding_access_checker.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/binding_access_checker.h"
+
+#include "base/strings/stringprintf.h"
+#include "gin/converter.h"
+
+namespace extensions {
+
+BindingAccessChecker::BindingAccessChecker(
+    const AvailabilityCallback& is_available)
+    : is_available_(is_available) {}
+BindingAccessChecker::~BindingAccessChecker() {}
+
+bool BindingAccessChecker::HasAccess(v8::Local<v8::Context> context,
+                                     const std::string& full_name) const {
+  return is_available_.Run(context, full_name);
+}
+
+bool BindingAccessChecker::HasAccessOrThrowError(
+    v8::Local<v8::Context> context,
+    const std::string& full_name) const {
+  if (!HasAccess(context, full_name)) {
+    context->GetIsolate()->ThrowException(v8::Exception::Error(gin::StringToV8(
+        context->GetIsolate(),
+        base::StringPrintf("'%s' is not available in this context.",
+                           full_name.c_str()))));
+    return false;
+  }
+
+  return true;
+}
+
+}  // namespace extensions