Prevent show a hidden status bar when opening modals, fix #7474

Summary:
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Closes the old #7474, keeping the status bar hidden when displaying a modal
or dialog, this is accomplished by verifying if the activity status bar is hidden or not.

Added a test to [RNTester](https://github.com/facebook/react-native/tree/master/RNTester), so it can be tested from there:

1. Run [RNTester](https://github.com/facebook/react-native/tree/master/RNTester) project
2. Go to <StatusBar> tests
3. Set `hidden: true` in the *StatusBar hidden* samples
4. Set `modal visible: true` and see the result

Here are some gifs to help see the results:
![fail](https://user-images.githubusercontent.com/1649955/36345378-f443ad7e-1407-11e8-850d-d6317fb34da4.gif)
![success](https://user-images.githubusercontent.com/1649955/36345392-1c590b56-1408-11e8-9244-a2e828f579ab.gif)

none

<!--
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  CATEGORY
[----------]        TYPE
[ CLI      ]   [-------------]      LOCATION
[ DOCS     ]   [ BREAKING    ]   [-------------]
[ GENERAL  ]   [ BUGFIX      ]   [-{Component}-]
[ INTERNAL ]   [ ENHANCEMENT ]   [ {File}      ]
[ IOS      ]   [ FEATURE     ]   [ {Directory} ]   |-----------|
[ ANDROID  ]   [ MINOR       ]   [ {Framework} ] - | {Message} |
[----------]   [-------------]   [-------------]   |-----------|

[ GENERAL  ]   [ BUGFIX      ]   [ [StatusBar] - Prevent show a hidden status bar when opening modals
 EXAMPLES:

 [IOS] [BREAKING] [FlatList] - Change a thing that breaks other things
 [ANDROID] [BUGFIX] [TextInput] - Did a thing to TextInput
 [CLI] [FEATURE] [local-cli/info/info.js] - CLI easier to do things with
 [DOCS] [BUGFIX] [GettingStarted.md] - Accidentally a thing/word
 [GENERAL] [ENHANCEMENT] [Yoga] - Added new yoga thing/position
 [INTERNAL] [FEATURE] [./scripts] - Added thing to script that nobody will see
-->
[ GENERAL  ]   [ BUGFIX      ]   [StatusBar] - Prevent show a hidden status bar when opening modals
Closes facebook/react-native#18004

Differential Revision: D7307564

Pulled By: hramos

fbshipit-source-id: 47e481ead78204865811ddf2ef3d27da77ad8b8f

js/StatusBarExample.js

@@ -17,6 +17,7 @@ const {
   Text,
   TouchableHighlight,
   View,
+  Modal,
 } = ReactNative;
 
 exports.framework = 'React';
@@ -100,6 +101,7 @@ class StatusBarHiddenExample extends React.Component<{}, $FlowFixMeState> {
             </Text>
           </View>
         </TouchableHighlight>
+        <ModalExample />
       </View>
     );
   }
@@ -380,6 +382,48 @@ class StatusBarStaticAndroidExample extends React.Component<{}> {
   }
 }
 
+
+class ModalExample extends React.Component<{}, $FlowFixMeState> {
+  state = {
+    modalVisible: false,
+  };
+
+  _onChangeModalVisible = () => {
+    this.setState({modalVisible: !this.state.modalVisible});
+  };
+
+  render() {
+    return (
+      <View>
+        <TouchableHighlight
+          style={styles.wrapper}
+          onPress={this._onChangeModalVisible}>
+          <View style={styles.button}>
+            <Text>modal visible: {this.state.hidden ? 'true' : 'false'}</Text>
+          </View>
+        </TouchableHighlight>
+        <Modal
+          visible={this.state.modalVisible}
+          transparent={true}
+          onRequestClose={this._onChangeModalVisible}>
+          <View style={[styles.container]}>
+            <View style={[styles.innerContainer]}>
+              <Text>This modal was presented!</Text>
+              <TouchableHighlight
+                onPress={this._onChangeModalVisible}
+                style={styles.modalButton}>
+                <View style={styles.button}>
+                  <Text>Close</Text>
+                </View>
+              </TouchableHighlight>
+            </View>
+          </View>
+        </Modal>
+      </View>
+    );
+  }
+}
+
 const examples = [{
   title: 'StatusBar hidden',
   render() {
@@ -436,6 +480,16 @@ const examples = [{
 exports.examples = examples;
 
 var styles = StyleSheet.create({
+  container: {
+    flex: 1,
+    justifyContent: 'center',
+    padding: 20,
+    backgroundColor: '#f5fcff'
+  },
+  innerContainer: {
+    borderRadius: 10,
+    alignItems: 'center',
+  },
   wrapper: {
     borderRadius: 5,
     marginBottom: 5,
@@ -449,5 +503,8 @@ var styles = StyleSheet.create({
     marginTop: 16,
     marginBottom: 8,
     fontWeight: 'bold',
-  }
+  },
+  modalButton: {
+    marginTop: 10,
+  },
 });