Enable the object-shorthand ESLint rule in src/display

Please see http://eslint.org/docs/rules/object-shorthand.

For the most part, these changes are of the search-and-replace kind, and the previously enabled `no-undef` rule should complement the tests in helping ensure that no stupid errors crept into to the patch.

src/display/text_layer.js

@@ -148,7 +148,7 @@ var renderTextLayer = (function renderTextLayerClosure() {
         bottom: b[3],
         div: textDiv,
         size: [divWidth, divHeight],
-        m: m
+        m,
       });
     }
   }