Added a new example for google signin.

google_signin/lib/user.dart

@@ -0,0 +1,39 @@
+import 'package:flutter/material.dart';
+import 'package:meta/meta.dart';
+import 'package:flutter/foundation.dart';
+import 'package:firebase_auth/firebase_auth.dart';
+
+class User extends StatelessWidget {
+  User({Key key, @required this.onLogout, @required this.user})
+      : super(key: key);
+
+  VoidCallback onLogout;
+  String username;
+  FirebaseUser user;
+
+  @override
+  Widget build(BuildContext context) {
+    return new Scaffold(
+      appBar: new AppBar(
+        title: new Text("Welcome"),
+        actions: <Widget>[
+          new IconButton(
+              icon: new Icon(Icons.exit_to_app), onPressed: this.onLogout)
+        ],
+      ),
+      body: new Container(
+          padding: const EdgeInsets.all(20.0),
+          child: new Center(
+              child: new Column(
+            mainAxisAlignment: MainAxisAlignment.center,
+            children: <Widget>[
+              new Image.network(user.photoUrl),
+              new Text(
+                user.displayName,
+                textScaleFactor: 1.5,
+              ),
+            ],
+          ))),
+    );
+  }
+}