[CRD iOS] Add the host setup instruction page

remoting/ios/app/host_collection_view_controller.h

 // 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.
 
 #ifndef REMOTING_IOS_APP_HOST_COLLECTION_VIEW_CONTOLLER_H_
 #define REMOTING_IOS_APP_HOST_COLLECTION_VIEW_CONTOLLER_H_
 
 #import <UIKit/UIKit.h>
 
 #import "ios/third_party/material_components_ios/src/components/Collections/src/MaterialCollections.h"
-#import "ios/third_party/material_components_ios/src/components/FlexibleHeader/src/MaterialFlexibleHeader.h"
 #import "remoting/ios/app/host_collection_view_cell.h"
 #import "remoting/ios/domain/host_info.h"
 
 // The host collection view controller delegate provides the data for available
 // hosts and receives selection events from the collection view controller.
 @protocol HostCollectionViewControllerDelegate<NSObject>
 
 // Notifies the delegate if a selection happens for the provided cell.
 // The delegate should run the completionBlock when processing for this event
 // has finished.
 @optional
 - (void)didSelectCell:(HostCollectionViewCell*)cell
            completion:(void (^)())completionBlock;
 
 // The delegate should provide the HostInfo object for the given path if
 // available from the cache.
 - (HostInfo*)getHostAtIndexPath:(NSIndexPath*)path;
 
 // The delegate must provide the total number of hosts currently cached.
 - (NSInteger)getHostCount;
 
 @end
 
 @interface HostCollectionViewController : MDCCollectionViewController
 
 @property(weak, nonatomic) id<HostCollectionViewControllerDelegate> delegate;
-@property(nonatomic)
-    MDCFlexibleHeaderContainerViewController* flexHeaderContainerViewController;
+@property(weak, nonatomic) id<UIScrollViewDelegate> scrollViewDelegate;
 
 @end
 
 #endif  // REMOTING_IOS_APP_HOST_LIST_VIEW_CONTOLLER_H_