[ios] RootCoordinator and view controller.

ios/clean/chrome/browser/ui/root/root_container_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/clean/chrome/browser/ui/root/root_container_view_controller.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+@implementation RootContainerViewController
+@synthesize contentViewController = _contentViewController;
+
+#pragma mark - UIViewController
+
+- (void)viewDidLoad {
+  [super viewDidLoad];
+  self.view.backgroundColor = [UIColor blackColor];
+  [self attachChildViewController:self.contentViewController];
+}
+
+#pragma mark - Public properties
+
+- (void)setContentViewController:(UIViewController*)contentViewController {
+  if (self.contentViewController == contentViewController)
+    return;
+  if ([self isViewLoaded]) {
+    [self detachChildViewController:self.contentViewController];
+    [self attachChildViewController:contentViewController];
+  }
+  _contentViewController = contentViewController;
+}
+
+#pragma mark - ChildViewController helper methods
+
+- (void)attachChildViewController:(UIViewController*)viewController {
+  if (!viewController) {
+    return;
+  }
+  [self addChildViewController:viewController];
+  viewController.view.autoresizingMask =
+      UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
+  viewController.view.frame = self.view.bounds;
+  [self.view addSubview:viewController.view];
+  [viewController didMoveToParentViewController:self];
+}
+
+- (void)detachChildViewController:(UIViewController*)viewController {
+  if (viewController.parentViewController != self)

[lpromero, 2017/04/11 15:20:39]

Should this be a DCHECK?

[edchin, 2017/04/11 15:52:05]

Yes, good suggestion. Will do.

[edchin, 2017/04/12 08:10:52]

Done.

+    return;
+  [viewController willMoveToParentViewController:nil];
+  [viewController.view removeFromSuperview];
+  [viewController removeFromParentViewController];
+}
+
+#pragma mark - ZoomTransitionDelegate
+
+- (CGRect)rectForZoomWithKey:(NSObject*)key inView:(UIView*)view {
+  if ([self.contentViewController
+          conformsToProtocol:@protocol(ZoomTransitionDelegate)]) {
+    return [static_cast<id<ZoomTransitionDelegate>>(self.contentViewController)

[lpromero, 2017/04/11 15:20:39]

Could you add a unit tests file for all new files?
Here you could test the public API simply by setting a contentViewController
(public property) and testing the ZoomTransitionDelegate protocol conformance
(public too).

[edchin, 2017/04/11 15:52:05]

Will do.

[edchin, 2017/04/12 08:10:52]

Done.

+        rectForZoomWithKey:key
+                    inView:view];
+  }
+  return CGRectNull;
+}
+
+@end