Add a showcase entry for the content widget.

ios/showcase/widget/sc_content_widget_coordinator.mm

Index: ios/showcase/widget/sc_content_widget_coordinator.mm
diff --git a/ios/showcase/widget/sc_content_widget_coordinator.mm b/ios/showcase/widget/sc_content_widget_coordinator.mm
new file mode 100644
index 0000000000000000000000000000000000000000..b58a321e1d52557af8f911e80c05b4f50764510e
--- /dev/null
+++ b/ios/showcase/widget/sc_content_widget_coordinator.mm
@@ -0,0 +1,25 @@
+// Copyright 2017 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.
+
+#import "ios/showcase/widget/sc_content_widget_coordinator.h"
+
+#import "ios/chrome/content_widget_extension/content_widget_view_controller.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+@implementation SCContentWidgetCoordinator
+
+@synthesize baseViewController;
+
+- (void)start {
+  ContentWidgetViewController* contentWidget =
+      [[ContentWidgetViewController alloc] init];
+  contentWidget.title = @"Content Widget";
+  contentWidget.view.backgroundColor = [UIColor whiteColor];
+  [self.baseViewController pushViewController:contentWidget animated:YES];
+}
+
+@end