[Extensions Binding] Allow for registering custom hooks

extensions/renderer/api_binding_hooks.cc

+// Copyright 2016 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_hooks.h"
+
+namespace extensions {
+
+APIBindingHooks::APIBindingHooks() {}
+APIBindingHooks::~APIBindingHooks() {}
+
+void APIBindingHooks::RegisterHandleRequest(const std::string& method_name,
+                                            const HandleRequestHook& hook) {
+  DCHECK(!hooks_used_) << "Hooks must be registered before the first use!";
+  request_hooks_[method_name] = hook;
+}
+
+APIBindingHooks::HandleRequestHook APIBindingHooks::GetHandleRequest(
+    const std::string& method_name) {
+  hooks_used_ = true;
+  auto iter = request_hooks_.find(method_name);
+  if (iter != request_hooks_.end())
+    return iter->second;
+
+  return HandleRequestHook();
+}
+
+}  // namespace extensions