Runtime: Fix unitFormatter with numberFormatter (2/2)

Ref #704
Ref #719

Author: rxaviers

src/common/runtime-stringify.js

@@ -2,8 +2,8 @@ define([], function( ) {
 
 return function( args ) {
 	return JSON.stringify( args, function( key, value ) {
-		if ( typeof value === "function" ) {
-			return value.runtimeKey; // if undefined, the value will be filtered out.
+		if ( value && value.runtimeKey ) {
+			return value.runtimeKey;
 		}
 		return value;
 	} );

src/number-runtime.js

@@ -29,10 +29,19 @@ Globalize._validateParameterPresence = validateParameterPresence;
 Globalize._validateParameterTypeNumber = validateParameterTypeNumber;
 Globalize._validateParameterTypeString = validateParameterTypeString;
 
+// Stamp runtimeKey and return cached fn.
+// Note, this function isn't made common to all formatters and parsers, because in practice this is
+// only used (at the moment) for numberFormatter used by unitFormatter.
+// TODO: Move this function into a common place when this is used by different formatters.
+function cached( runtimeKey ) {
+	Globalize[ runtimeKey ].runtimeKey = runtimeKey;
+	return Globalize[ runtimeKey ];
+}
+
 Globalize.numberFormatter =
 Globalize.prototype.numberFormatter = function( options ) {
 	options = options || {};
-	return Globalize[ runtimeKey( "numberFormatter", this._locale, [ options ] ) ];
+	return cached( runtimeKey( "numberFormatter", this._locale, [ options ] ) );
 };
 
 Globalize.numberParser =