Adjust the brace-style ESLint rule to disallow single lines (and also enable no-iterator)

See http://eslint.org/docs/rules/brace-style.
Having the opening/closing braces on the same line can often make the code slightly more difficult to read, in particular for `if`/`else if` statements, compared to using new lines.

This patch also, for consistency with `mozilla-central`, enables the [`no-iterator`](http://eslint.org/docs/rules/no-iterator) rule. Note that this rule didn't require a single code change.

src/display/dom_utils.js

@@ -98,7 +98,9 @@ if (typeof PDFJSDev === 'undefined' ||
     return (typeof imageData.data.buffer !== 'undefined');
   };
 } else {
-  hasCanvasTypedArrays = function () { return true; };
+  hasCanvasTypedArrays = function () {
+    return true;
+  };
 }
 
 var LinkTarget = {