refactor($interpolate): move standalone functions to the service scope

Closes #10413

Author: jbedard

src/ng/interpolate.js

@@ -88,6 +88,28 @@ function $InterpolateProvider() {
       return '\\\\\\' + ch;
     }
 
+    function unescapeText(text) {
+      return text.replace(escapedStartRegexp, startSymbol).
+        replace(escapedEndRegexp, endSymbol);
+    }
+
+    function stringify(value) {
+      if (value == null) { // null || undefined
+        return '';
+      }
+      switch (typeof value) {
+        case 'string':
+          break;
+        case 'number':
+          value = '' + value;
+          break;
+        default:
+          value = toJson(value);
+      }
+
+      return value;
+    }
+
     /**
      * @ngdoc service
      * @name $interpolate
@@ -243,23 +265,6 @@ function $InterpolateProvider() {
             $sce.valueOf(value);
         };
 
-        var stringify = function(value) {
-          if (value == null) { // null || undefined
-            return '';
-          }
-          switch (typeof value) {
-            case 'string':
-              break;
-            case 'number':
-              value = '' + value;
-              break;
-            default:
-              value = toJson(value);
-          }
-
-          return value;
-        };
-
         return extend(function interpolationFn(context) {
             var i = 0;
             var ii = expressions.length;
@@ -294,11 +299,6 @@ function $InterpolateProvider() {
         });
       }
 
-      function unescapeText(text) {
-        return text.replace(escapedStartRegexp, startSymbol).
-          replace(escapedEndRegexp, endSymbol);
-      }
-
       function parseStringifyInterceptor(value) {
         try {
           value = getValue(value);