[fix] AppRegistry container layout

Absolute fill positioning provides better default layout for full-screen
apps.

Fix #528

docs/apis/AppRegistry.md

@@ -40,6 +40,9 @@ Runs the application that was registered under `appKey`. The `appParameters`
 must include the `rootTag` into which the application is rendered, and
 optionally any `initialProps`.
 
+On web, if the `rootTag` is a sub-section of your application it should be
+styled as `position:relative` and given an explicit height.
+
 static **unmountApplicationComponentAtRootTag**(rootTag: HTMLElement)
 
 To "stop" an application when a view should be destroyed, call

src/apis/AppRegistry/AppContainer.js

@@ -48,7 +48,7 @@ export default class AppContainer extends Component {
 
   render() {
     return (
-      <View pointerEvents="box-none" style={styles.appContainer}>
+      <View pointerEvents="box-none" style={[styles.appContainer, StyleSheet.absoluteFill]}>
         <View
           children={this.props.children}
           key={this.state.mainKey}

src/apis/StyleSheet/createReactDOMStyle.js

@@ -152,7 +152,7 @@ const createReducer = (style, styleProps) => {
             resolvedStyle.flexShrink = 0;
           }
           if (style.flexBasis == null) {
-            resolvedStyle.flexBasis = 'auto'
+            resolvedStyle.flexBasis = 'auto';
           }
         }
         break;