Avoid type coercion of size in _.chunk unless needed.

lodash.js

@@ -3125,7 +3125,7 @@
     /*--------------------------------------------------------------------------*/
 
     /**
-     * Creates an array of elements split into groups the length of `chunkSize`.
+     * Creates an array of elements split into groups the length of `size`.
      * If `collection` can't be split evenly, the final chunk will be the remaining
      * elements.
      *
@@ -3133,7 +3133,7 @@
      * @memberOf _
      * @category Array
      * @param {Array} array The array to process.
-     * @param {numer} [chunkSize=1] The size of each chunk.
+     * @param {numer} [size=1] The length of each chunk.
      * @returns {Array} Returns the new array containing chunks.
      * @example
      *
@@ -3143,15 +3143,15 @@
      * _.chunk(['a', 'b', 'c', 'd'], 3);
      * // => [['a', 'b', 'c'], ['d']]
      */
-    function chunk(array, chunkSize) {
+    function chunk(array, size) {
       var index = 0,
           length = array ? array.length : 0,
           resIndex = -1,
           result = [];
 
-      chunkSize = nativeMax(+chunkSize || 1, 1);
+      size = typeof size == 'undefined' ? 1 : nativeMax(+size || 1, 1);
       while (index < length) {
-        result[++resIndex] = slice(array, index, (index += chunkSize));
+        result[++resIndex] = slice(array, index, (index += size));
       }
       return result;
     }