[AppBar] Remove unnecessary logic in setContentViewController:

Summary: Closes https://github.com/google/material-components-ios/issues/287.

Reviewers: #mdc_ios_owners, ajsecord

Reviewed By: #mdc_ios_owners, ajsecord

Projects: #material_components_ios

Differential Revision: http://codereview.cc/D490

components/AppBar/src/MDCAppBarContainerViewController.m

@@ -98,13 +98,12 @@ - (void)setContentViewController:(UIViewController *)contentViewController {
   _contentViewController = contentViewController;
 
   [self addChildViewController:contentViewController];
-  if ([self isViewLoaded]) {
-    [self.view insertSubview:contentViewController.view
-                belowSubview:self.appBar.headerViewController.headerView];
-    [contentViewController didMoveToParentViewController:self];
 
-    [_appBar.navigationBar observeNavigationItem:_contentViewController.navigationItem];
-  }
+  NSAssert(![self isViewLoaded],
+           @"View should not have been loaded at this point."
+           @" Verify that the view is not being accessed anywhere in %@ or %@.",
+           NSStringFromSelector(_cmd),
+           NSStringFromSelector(@selector(initWithContentViewController:)));
 }
 
 @end

components/AppBar/tests/unit/AppBarContainerIssue287Tests.swift

@@ -0,0 +1,37 @@
+/*
+Copyright 2016-present Google Inc. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import XCTest
+import MaterialComponents
+
+// Tests confirming that MDCAppBarContainerViewController doesn't loads its own view during
+// initialization.
+//
+// Based on issue https://github.com/google/material-components-ios/issues/287
+class AppBarContainerIssue287Tests: XCTestCase {
+
+  var content: UIViewController!
+  var container: MDCAppBarContainerViewController!
+
+  override func setUp() {
+    content = UIViewController()
+    container = MDCAppBarContainerViewController(contentViewController: content)
+  }
+
+  func testViewHasNotLoadedAfterInitialization() {
+    XCTAssertFalse(container.isViewLoaded())
+  }
+}