Add a fake cursor (blinking UIView) to the widget extension.

ios/chrome/widget_extension/widget_view_controller.mm

 // 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/chrome/widget_extension/widget_view_controller.h"
 
 #import <NotificationCenter/NotificationCenter.h>
 
 #import "ios/chrome/widget_extension/widget_view.h"
 
@@ skipping 12 matching lines @@
 #pragma mark - UIViewController
 
 - (void)viewDidLoad {
   [super viewDidLoad];
 
   // A local variable is necessary here as the property is declared weak and the
   // object would be deallocated before being retained by the addSubview call.
   WidgetView* widgetView = [[WidgetView alloc] init];
   self.widgetView = widgetView;
   [self.view addSubview:self.widgetView];
+
+  [self.widgetView setTranslatesAutoresizingMaskIntoConstraints:NO];
+  [NSLayoutConstraint activateConstraints:@[
+    [self.widgetView.leadingAnchor
+        constraintEqualToAnchor:[self.view leadingAnchor]],
+    [self.widgetView.trailingAnchor
+        constraintEqualToAnchor:[self.view trailingAnchor]],
+    [self.widgetView.heightAnchor
+        constraintEqualToAnchor:[self.view heightAnchor]],
+    [self.widgetView.widthAnchor
+        constraintEqualToAnchor:[self.view widthAnchor]]
+  ]];
 }
 
 @end