Fix disappearing omnibox on iPhone X.

The old-school layout logic in BVC was also re-inserting views on each
update, which is unnecessary, and in some cases causes views to show up
in the wrong z-order.  Insert only needs to happen on initial layout,
so gating this in a flag should fix the issues.

Bug: 782373
Change-Id: I326f3b9199717c0ad014267fa0239581574a826d
Reviewed-on: https://chromium-review.googlesource.com/763711
Reviewed-by: Stepan Khapugin <stkhapugin@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#515987}

diff --git a/ios/chrome/browser/ui/browser_view_controller.mm b/ios/chrome/browser/ui/browser_view_controller.mm
index 3133b2a6..c5bdd7f5 100644
--- a/ios/chrome/browser/ui/browser_view_controller.mm
+++ b/ios/chrome/browser/ui/browser_view_controller.mm

@@ -686,8 +686,9 @@
 // Updates view-related functionality with the given tab model and browser
 // state. The view must have been loaded.  Uses |_browserState| and |_model|.
 - (void)addUIFunctionalityForModelAndBrowserState;
-// Sets the correct frame and hierarchy for subviews and helper views.
-- (void)setUpViewLayout;
+// Sets the correct frame and hierarchy for subviews and helper views.  Only
+// insert views on |initialLayout|.
+- (void)setUpViewLayout:(BOOL)initialLayout;
 // Makes |tab| the currently visible tab, displaying its view.  Calls
 // -selectedTabChanged on the toolbar only if |newSelection| is YES.
 - (void)displayTab:(Tab*)tab isNewSelection:(BOOL)newSelection;
@@ -1308,7 +1309,7 @@
   // Install fake status bar for iPad iOS7
   [self installFakeStatusBar];
   [self buildToolbarAndTabStrip];
-  [self setUpViewLayout];
+  [self setUpViewLayout:YES];
   if (IsSafeAreaCompatibleToolbarEnabled()) {
     [self addConstraintsToToolbar];
   }
@@ -1331,7 +1332,7 @@
   // Gate this behind iPhone X, since it's currently the only device that
   // needs layout updates here after startup.
   if (IsIPhoneX()) {
-    [self setUpViewLayout];
+    [self setUpViewLayout:NO];
   }
   if (IsSafeAreaCompatibleToolbarEnabled()) {
     // TODO(crbug.com/778236): Check if this call can be removed once the
@@ -2042,7 +2043,7 @@
 }
 
 // Set the frame for the various views. View must be loaded.
-- (void)setUpViewLayout {
+- (void)setUpViewLayout:(BOOL)initialLayout {
   DCHECK([self isViewLoaded]);
   CGFloat widthOfView = CGRectGetWidth([self view].bounds);
   CGFloat minY = [self headerOffset];
@@ -2058,7 +2059,8 @@
 
   // Position the toolbar next, either at the top of the browser view or
   // directly under the tabstrip.
-  [self addChildViewController:_toolbarCoordinator.toolbarViewController];
+  if (initialLayout)
+    [self addChildViewController:_toolbarCoordinator.toolbarViewController];
   CGRect toolbarFrame = _toolbarCoordinator.toolbarViewController.view.frame;
   toolbarFrame.origin = CGPointMake(0, minY);
   toolbarFrame.size.width = widthOfView;
@@ -2068,14 +2070,17 @@
 
   // Place the infobar container above the content area.
   InfoBarContainerView* infoBarContainerView = _infoBarContainer->view();
-  [self.view insertSubview:infoBarContainerView aboveSubview:_contentArea];
+  if (initialLayout)
+    [self.view insertSubview:infoBarContainerView aboveSubview:_contentArea];
 
   // Place the toolbar controller above the infobar container.
-  [[self view] insertSubview:_toolbarCoordinator.toolbarViewController.view
-                aboveSubview:infoBarContainerView];
+  if (initialLayout)
+    [[self view] insertSubview:_toolbarCoordinator.toolbarViewController.view
+                  aboveSubview:infoBarContainerView];
   minY += CGRectGetHeight(toolbarFrame);
-  [_toolbarCoordinator.toolbarViewController
-      didMoveToParentViewController:self];
+  if (initialLayout)
+    [_toolbarCoordinator.toolbarViewController
+        didMoveToParentViewController:self];
 
   // Account for the toolbar's drop shadow.  The toolbar overlaps with the web
   // content slightly.
@@ -2098,7 +2103,8 @@
 
   // Attach the typing shield to the content area but have it hidden.
   [_typingShield setFrame:[_contentArea frame]];
-  [[self view] insertSubview:_typingShield aboveSubview:_contentArea];
+  if (initialLayout)
+    [[self view] insertSubview:_typingShield aboveSubview:_contentArea];
   [_typingShield setHidden:YES];
   _typingShield.accessibilityIdentifier = @"Typing Shield";
   _typingShield.accessibilityLabel = l10n_util::GetNSString(IDS_CANCEL);