Upstream Chrome on iOS source code [5/11].

ios/chrome/browser/ui/main/main_coordinator.mm

+// Copyright 2016 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/browser/ui/main/main_coordinator.h"
+
+#include "base/ios/weak_nsobject.h"
+#include "base/mac/scoped_nsobject.h"
+#import "ios/chrome/browser/ui/main/main_view_controller.h"
+
+@interface MainCoordinator () {
+  // Instance variables backing properties of the same name.
+  // |_mainViewController| will be owned by |self.window|.
+  base::WeakNSObject<MainViewController> _mainViewController;
+}
+
+@end
+
+@implementation MainCoordinator
+
+#pragma mark - property implementation.
+
+- (MainViewController*)mainViewController {
+  return _mainViewController;
+}
+
+#pragma mark - ChromeCoordinator implementation.
+
+- (void)start {
+  base::scoped_nsobject<MainViewController> mainViewController(
+      [[MainViewController alloc] init]);
+  _mainViewController.reset(mainViewController);
+  self.window.rootViewController = self.mainViewController;
+
+  // Size the main view controller to fit the whole screen.
+  [self.mainViewController.view setFrame:self.window.bounds];
+}
+
+@end