extend size() to take ownPropsOnly param

- extend size() to take size(obj, ownPropsOnly)
- add specs for size()
- update docs to mention string support
- use size() in ng:repeat

including the hasOwnProp check for all object doesn't create
significant perf penalty:
http://jsperf.com/dedicated-code-branch-for-hasownprop

src/Angular.js

@@ -461,12 +461,14 @@ function map(obj, iterator, context) {
  * @function
  *
  * @description
- * Determines the number of elements in an array or number of properties of an object.
+ * Determines the number of elements in an array, number of properties of an object or string
+ * length.
  *
  * Note: this function is used to augment the Object type in angular expressions. See
  * {@link angular.Object} for more info.
  *
- * @param {Object|Array} obj Object or array to inspect.
+ * @param {Object|Array|string} obj Object, array or string to inspect.
+ * @param {boolean} [ownPropsOnly=false] Count only "own" properties in an object
  * @returns {number} The size of `obj` or `0` if `obj` is neither an object or an array.
  *
  * @example
@@ -483,14 +485,15 @@ function map(obj, iterator, context) {
  *  </doc:scenario>
  * </doc:example>
  */
-function size(obj) {
+function size(obj, ownPropsOnly) {
   var size = 0, key;
   if (obj) {
     if (isNumber(obj.length)) {
       return obj.length;
     } else if (isObject(obj)){
       for (key in obj)
-        size++;
+        if (!ownPropsOnly || obj.hasOwnProperty(key))
+          size++;
     }
   }
   return size;

src/widgets.js

@@ -913,19 +913,10 @@ angularWidget('@ng:repeat', function(expression, element){
           childCount = children.length,
           lastIterElement = iterStartElement,
           collection = this.$tryEval(rhs, iterStartElement),
-          is_array = isArray(collection),
-          collectionLength = 0,
+          collectionLength = size(collection, true),
           childScope,
           key;
 
-      if (is_array) {
-        collectionLength = collection.length;
-      } else {
-        for (key in collection)
-          if (collection.hasOwnProperty(key))
-            collectionLength++;
-      }
-
       for (key in collection) {
         if (collection.hasOwnProperty(key)) {
           if (index < childCount) {

test/AngularSpec.js

@@ -110,6 +110,32 @@ describe('angular', function(){
     });
   });
 
+
+  describe('size', function() {
+    it('should return the number of items in an array', function() {
+      expect(size([])).toBe(0);
+      expect(size(['a', 'b', 'c'])).toBe(3);
+    });
+
+    it('should return the number of properties of an object', function() {
+      expect(size({})).toBe(0);
+      expect(size({a:1, b:'a', c:noop})).toBe(3);
+    });
+
+    it('should return the number of own properties of an object', function() {
+      var obj = inherit({protoProp: 'c', protoFn: noop}, {a:1, b:'a', c:noop});
+
+      expect(size(obj)).toBe(5);
+      expect(size(obj, true)).toBe(3);
+    });
+
+    it('should return the string length', function() {
+      expect(size('')).toBe(0);
+      expect(size('abc')).toBe(3);
+    });
+  });
+
+
   describe('parseKeyValue', function() {
     it('should parse a string into key-value pairs', function() {
       expect(parseKeyValue('')).toEqual({});