[win] Add signin support for the app launcher.

ui/app_list/views/signin_view.cc

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ui/app_list/views/signin_view.h"
+
+#include "content/public/browser/web_contents.h"
+#include "ui/app_list/signin_delegate.h"
+#include "ui/views/controls/webview/webview.h"
+#include "ui/views/layout/fill_layout.h"
+
+namespace app_list {
+
+SigninView::SigninView(SigninDelegate* delegate)
+    : web_view_(new views::WebView(NULL)), delegate_(delegate) {
+  SetLayoutManager(new views::FillLayout());
+  AddChildView(web_view_);
+}
+
+SigninView::~SigninView() {
+  web_view_->SetWebContents(NULL);
+}
+
+void SigninView::BeginSignin() {
+  if (!delegate_)
+    return;
+
+  web_contents_.reset(delegate_->PrepareForSignin());
+  web_view_->SetWebContents(web_contents_.get());
+}
+
+}  // namespace app_list