Move const PortName data out of header file

mojo/edk/system/ports/name.h

Index: mojo/edk/system/ports/name.h
diff --git a/mojo/edk/system/ports/name.h b/mojo/edk/system/ports/name.h
index 1082719f6df5f29c37d3a6bb6df00fc8a78514fd..2e74cd58e534eb1e21bce9cc5399142d91aa5ced 100644
--- a/mojo/edk/system/ports/name.h
+++ b/mojo/edk/system/ports/name.h
@@ -17,7 +17,7 @@ namespace edk {
 namespace ports {
 
 struct Name {
-  Name(uint64_t v1, uint64_t v2) : v1(v1), v2(v2) {}
+  constexpr Name(uint64_t v1, uint64_t v2) : v1(v1), v2(v2) {}
   uint64_t v1, v2;
 };
 
@@ -36,18 +36,19 @@ inline bool operator<(const Name& a, const Name& b) {
 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) {}
+  constexpr PortName() : Name(0, 0) {}
+  constexpr PortName(uint64_t v1, uint64_t v2) : Name(v1, v2) {}
 };
 
-const PortName kInvalidPortName = {0, 0};
-
 struct NodeName : Name {
-  NodeName() : Name(0, 0) {}
-  NodeName(uint64_t v1, uint64_t v2) : Name(v1, v2) {}
+  constexpr NodeName() : Name(0, 0) {}
+  constexpr NodeName(uint64_t v1, uint64_t v2) : Name(v1, v2) {}
 };
 
-const NodeName kInvalidNodeName = {0, 0};
+struct constants {
+  static constexpr PortName kInvalidPortName = {0, 0};
+  static constexpr NodeName kInvalidNodeName = {0, 0};
+};
 
 }  // namespace ports
 }  // namespace edk