Upstream Chrome on iOS source code [4/11].

ios/chrome/browser/ui/browser_container_view.mm

+// Copyright 2015 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/browser_container_view.h"
+
+#import "base/ios/weak_nsobject.h"
+
+@implementation BrowserContainerView {
+  // Weak reference to content view, so old _contentView can be removed from
+  // superview when new one is added.
+  base::WeakNSObject<UIView> _contentView;
+}
+
+- (void)dealloc {
+  DCHECK(![_contentView superview] || [_contentView superview] == self);
+
+  [super dealloc];
+}
+
+- (void)displayContentView:(UIView*)contentView {
+  DCHECK(![_contentView superview] || [_contentView superview] == self);
+  [_contentView removeFromSuperview];
+  _contentView.reset(contentView);
+
+  if (contentView) {
+    [self addSubview:contentView];
+  }
+}
+
+@end