[Extensions Bindings] Fix uninitialized member in ArgumentSpec

extensions/renderer/argument_spec.h

 // 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.
 
 #ifndef EXTENSIONS_RENDERER_ARGUMENT_SPEC_H_
 #define EXTENSIONS_RENDERER_ARGUMENT_SPEC_H_
 
 #include <map>
 #include <memory>
 #include <set>
@@ skipping 103 matching lines @@
                           std::string* error) const;
 
   // Returns an error message indicating the type of |value| does not match the
   // expected type.
   std::string GetInvalidTypeError(v8::Local<v8::Value> value) const;
 
   // The name of the argument.
   std::string name_;
 
   // The type of the argument.
-  ArgumentType type_;
+  ArgumentType type_ = ArgumentType::INTEGER;
 
   // Whether or not the argument is required.
-  bool optional_;
+  bool optional_ = false;
 
   // Whether to preserve null properties found in objects.
-  bool preserve_null_;
+  bool preserve_null_ = false;
 
   // The reference the argument points to, if any. Note that if this is set,
   // none of the following fields describing the argument will be.
   base::Optional<std::string> ref_;
 
   // The type of instance an object should be, if any. Only applicable for
   // ArgumentType::OBJECT. If specified, the argument must contain the instance
   // type in its prototype chain.
   base::Optional<std::string> instance_of_;
 
@@ skipping 25 matching lines @@
   // to allow the API to pass an object with arbitrary properties. Only
   // applicable for ArgumentType::OBJECT.
   std::unique_ptr<ArgumentSpec> additional_properties_;
 
   DISALLOW_COPY_AND_ASSIGN(ArgumentSpec);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_RENDERER_ARGUMENT_SPEC_H_