[fix] ScrollView style issues

* Fix contentContainer not expanding to contain all child elements
* Add momentum scrolling on iOS

Fix #197

examples/components/ScrollView/ScrollViewExample.js

@@ -52,6 +52,7 @@ const styles = StyleSheet.create({
     borderWidth: '1px'
   },
   scrollViewContentContainerStyle: {
+    backgroundColor: '#eee',
     padding: '10px'
   }
 })

src/apis/StyleSheet/StyleSheetValidation.js

@@ -74,7 +74,8 @@ StyleSheetValidation.addValidStylePropTypes({
   display: PropTypes.string,
   float: PropTypes.oneOf([ 'left', 'none', 'right' ]),
   font: PropTypes.string, /* @private */
-  listStyle: PropTypes.string
+  listStyle: PropTypes.string,
+  WebkitOverflowScrolling: PropTypes.string /* @private */
 })
 
 module.exports = StyleSheetValidation

src/components/ScrollView/index.js

@@ -222,14 +222,16 @@ const styles = StyleSheet.create({
   base: {
     flex: 1,
     overflowX: 'hidden',
-    overflowY: 'auto'
+    overflowY: 'auto',
+    WebkitOverflowScrolling: 'touch'
   },
   baseHorizontal: {
+    flexDirection: 'row',
     overflowX: 'auto',
     overflowY: 'hidden'
   },
   contentContainer: {
-    flex: 1
+    flexGrow: 1
   },
   contentContainerHorizontal: {
     flexDirection: 'row'

src/components/View/ViewStylePropTypes.js

@@ -16,6 +16,7 @@ module.exports = {
   backgroundColor: ColorPropType,
   opacity: number,
   overflow: autoOrHiddenOrVisible,
+  zIndex: number,
   /*
    * @platform web
    */
@@ -34,5 +35,5 @@ module.exports = {
   transition: string,
   userSelect: string,
   visibility: hiddenOrVisible,
-  zIndex: number
+  WebkitOverflowScrolling: oneOf([ 'auto', 'touch' ])
 };