Upstream Chrome on iOS source code [9/11].

ios/chrome/browser/ui/tab_switcher/tab_switcher_panel_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/tab_switcher/tab_switcher_panel_view.h"
+
+#import "base/mac/scoped_nsobject.h"
+#import "ios/chrome/browser/ui/tab_switcher/tab_switcher_panel_cell.h"
+#import "ios/chrome/browser/ui/tab_switcher/tab_switcher_panel_collection_view_layout.h"
+
+@interface TabSwitcherPanelView () {
+  base::scoped_nsobject<UICollectionView> _collectionView;
+  base::scoped_nsobject<TabSwitcherPanelCollectionViewLayout>
+      _collectionViewLayout;
+  ios_internal::SessionType _sessionType;
+}
+
+@end
+
+@implementation TabSwitcherPanelView
+
+- (instancetype)initWithSessionType:(ios_internal::SessionType)sessionType {
+  self = [super initWithFrame:CGRectZero];
+  if (self) {
+    _sessionType = sessionType;
+    [self loadSubviews];
+  }
+  return self;
+}
+
+- (instancetype)initWithFrame:(CGRect)frame {
+  NOTREACHED();
+  return nil;
+}
+
+- (instancetype)initWithCoder:(NSCoder*)aDecoder {
+  NOTREACHED();
+  return nil;
+}
+
+- (UICollectionView*)collectionView {
+  return _collectionView;
+}
+
+- (void)updateCollectionLayoutWithCompletion:(void (^)(void))completion {
+  [_collectionView performBatchUpdates:nil
+                            completion:^(BOOL) {
+                              if (completion)
+                                completion();
+                            }];
+}
+
+- (CGSize)cellSize {
+  return [_collectionViewLayout itemSize];
+}
+
+#pragma mark - Private
+
+- (void)loadSubviews {
+  _collectionViewLayout.reset(
+      [[TabSwitcherPanelCollectionViewLayout alloc] init]);
+  _collectionView.reset([[UICollectionView alloc]
+             initWithFrame:self.bounds
+      collectionViewLayout:_collectionViewLayout.get()]);
+  if (_sessionType == ios_internal::SessionType::DISTANT_SESSION) {
+    [_collectionView registerClass:[TabSwitcherDistantSessionCell class]
+        forCellWithReuseIdentifier:[TabSwitcherDistantSessionCell identifier]];
+  } else {
+    [_collectionView registerClass:[TabSwitcherLocalSessionCell class]
+        forCellWithReuseIdentifier:[TabSwitcherLocalSessionCell identifier]];
+  }
+  [_collectionView setBackgroundColor:[UIColor clearColor]];
+  [self addSubview:_collectionView];
+  [_collectionView setAutoresizingMask:UIViewAutoresizingFlexibleHeight |
+                                       UIViewAutoresizingFlexibleWidth];
+}
+
+@end