[Extensions Bindings] Add native declarativeContent verification

extensions/renderer/api_binding.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.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/logging.h"
@@ skipping 358 matching lines @@
                        gin::StringToSymbol(isolate, enum_entry.first));
     }
     object_template->Set(isolate, entry.first.c_str(), enum_object);
   }
 
   if (property_definitions_) {
     DecorateTemplateWithProperties(isolate, object_template,
                                    *property_definitions_);
   }
 
+  // Allow custom bindings a chance to tweak the template, such as to add
+  // additional properties or types.
+  binding_hooks_->InitializeTemplate(isolate, object_template, *type_refs_);
+
   object_template_.Set(isolate, object_template);
 }
 
 void APIBinding::DecorateTemplateWithProperties(
     v8::Isolate* isolate,
     v8::Local<v8::ObjectTemplate> object_template,
     const base::DictionaryValue& properties) {
   static const char kValueKey[] = "value";
   for (base::DictionaryValue::Iterator iter(properties); !iter.IsAtEnd();
        iter.Advance()) {
@@ skipping 191 matching lines @@
     arguments->ThrowTypeError("Invalid invocation");
     return;
   }
 
   request_handler_->StartRequest(context, name, std::move(converted_arguments),
                                  callback, custom_callback,
                                  binding::RequestThread::UI);
 }
 
 }  // namespace extensions