Add keys to hash as you need them.

Summary:
Just showing a hash of values is misleading. Makes the user think you can just pass in the values without the keys.
Closes https://github.com/facebook/react-native/pull/7310

Differential Revision: D3245834

fb-gh-sync-id: 39220ed7720e3ff402f2c2ba8bebdefb96bfa203
fbshipit-source-id: 39220ed7720e3ff402f2c2ba8bebdefb96bfa203

Libraries/Components/ScrollView/ScrollView.js

@@ -63,7 +63,7 @@ var ScrollView = React.createClass({
     automaticallyAdjustContentInsets: PropTypes.bool,
     /**
      * The amount by which the scroll view content is inset from the edges
-     * of the scroll view. Defaults to `{0, 0, 0, 0}`.
+     * of the scroll view. Defaults to `{top: 0, left: 0, bottom: 0, right: 0}`.
      * @platform ios
      */
     contentInset: EdgeInsetsPropType,