Update the path-provider example

Make changes to the external storage directory component of the
path provider platform.

Author: natelust

packages/path-provider/example/lib/main.dart

@@ -68,8 +68,7 @@ class _MyHomePageState extends State<MyHomePage> {
 
   void _requestExternalStorageDirectory() {
     setState(() {
-      if (Platform.operatingSystem != "ios")
-        _externalDocumentsDirectory = getExternalStorageDirectory();
+      _externalDocumentsDirectory = getExternalStorageDirectory();
     });
   }
 
@@ -113,16 +112,17 @@ class _MyHomePageState extends State<MyHomePage> {
               child: new FutureBuilder<Directory>(
                   future: _appDocumentsDirectory, builder: _buildDirectory),
             ),
-            new Cloumn(
+            new Column(
               children : <Widget>[
                 new Padding(
-                  padding: const EdgeInserts.add(16.0),
+                  padding: const EdgeInsets.all(16.0),
                   child: new RaisedButton(
-                    child: const Test('${Platform.operatingSystem != "ios" ?
-                                      "Get External Storage Directory" :
-                                      "External Directories are unavailable " +
-                                      "on iOS"}'),
-                    onPressed: _requestExternalStorageDirectory,
+                    child: new Text('${Platform.isIOS ?
+                                    "External directories are unavailable " +
+                                    "on iOS":
+                                    "Get External Storage Directory" }'),
+                    onPressed: Platform.isIOS ? null :
+                      _requestExternalStorageDirectory,
                   ),
                 ),
               ]