[CRD iOS] Fix shadow between host cards and use anchor constraints

remoting/ios/app/host_collection_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.
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 #import "remoting/ios/app/host_collection_view_controller.h"
 
@@ skipping 31 matching lines @@
                                            [HostCollectionViewCell class])];
   }
   return self;
 }
 
 #pragma mark - UIViewController
 
 - (void)viewDidLoad {
   [super viewDidLoad];
   self.styler.cellStyle = MDCCollectionViewCellStyleCard;
-  self.styler.cellLayoutType = MDCCollectionViewCellLayoutTypeGrid;
-  self.styler.gridPadding = 0;
-  self.styler.gridColumnCount = 1;
+  self.styler.cellLayoutType = MDCCollectionViewCellLayoutTypeList;
 }
 
 - (void)viewWillTransitionToSize:(CGSize)size
        withTransitionCoordinator:
            (id<UIViewControllerTransitionCoordinator>)coordinator {
   [self.collectionView.collectionViewLayout invalidateLayout];
 }
 
 - (void)viewWillAppear:(BOOL)animated {
   [super viewWillAppear:animated];
@@ skipping 78 matching lines @@
   // Use a custom shadow under the flexible header.
   MDCShadowLayer* shadowLayer = [MDCShadowLayer layer];
   [headerView setShadowLayer:shadowLayer
       intensityDidChangeBlock:^(CALayer* layer, CGFloat intensity) {
         CGFloat elevation = MDCShadowElevationAppBar * intensity;
         [(MDCShadowLayer*)layer setElevation:elevation];
       }];
 }
 
 @end