Move const PortName data out of header file

mojo/edk/system/ports/name.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 MOJO_EDK_SYSTEM_PORTS_NAME_H_
 #define MOJO_EDK_SYSTEM_PORTS_NAME_H_
 
 #include <stdint.h>
 
 #include <ostream>
@@ skipping 22 matching lines @@
   return std::tie(a.v1, a.v2) < std::tie(b.v1, b.v2);
 }
 
 std::ostream& operator<<(std::ostream& stream, const Name& name);
 
 struct PortName : Name {
   PortName() : Name(0, 0) {}
   PortName(uint64_t v1, uint64_t v2) : Name(v1, v2) {}
 };
 
-const PortName kInvalidPortName = {0, 0};
+extern const PortName kInvalidPortName;
 
 struct NodeName : Name {
   NodeName() : Name(0, 0) {}
   NodeName(uint64_t v1, uint64_t v2) : Name(v1, v2) {}
 };
 
-const NodeName kInvalidNodeName = {0, 0};
+extern const NodeName kInvalidNodeName;
 
 }  // namespace ports
 }  // namespace edk
 }  // namespace mojo
 
 namespace std {
 
 template <>
 struct hash<mojo::edk::ports::PortName> {
   std::size_t operator()(const mojo::edk::ports::PortName& name) const {
     return base::HashInts64(name.v1, name.v2);
   }
 };
 
 template <>
 struct hash<mojo::edk::ports::NodeName> {
   std::size_t operator()(const mojo::edk::ports::NodeName& name) const {
     return base::HashInts64(name.v1, name.v2);
   }
 };
 
 }  // namespace std
 
 #endif  // MOJO_EDK_SYSTEM_PORTS_NAME_H_