Upstream Chrome on iOS source code [4/11].

ios/chrome/browser/ui/collection_view/cells/MDCCollectionViewCell+Chrome.mm

Index: ios/chrome/browser/ui/collection_view/cells/MDCCollectionViewCell+Chrome.mm
diff --git a/ios/chrome/browser/ui/collection_view/cells/MDCCollectionViewCell+Chrome.mm b/ios/chrome/browser/ui/collection_view/cells/MDCCollectionViewCell+Chrome.mm
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index 0000000000000000000000000000000000000000..52f4e5ff3839817dafa2e2af8b281e8d4b279a2b
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+++ b/ios/chrome/browser/ui/collection_view/cells/MDCCollectionViewCell+Chrome.mm
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+// Copyright 2016 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/collection_view/cells/MDCCollectionViewCell+Chrome.h"
+
+#import "ios/chrome/browser/ui/collection_view/cells/collection_view_item.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+@implementation MDCCollectionViewCell (Chrome)
+
++ (CGFloat)cr_preferredHeightForWidth:(CGFloat)targetWidth
+                              forItem:(CollectionViewItem*)item {
+  // Dictionary where keys are class names and values are sizing cells.
+  static NSMutableDictionary<NSString*, MDCCollectionViewCell*>*
+      gSharedSizingCells;
+  static dispatch_once_t onceToken;
+  dispatch_once(&onceToken, ^{
+    gSharedSizingCells = [NSMutableDictionary dictionary];
+  });
+
+  // Get the sizing cell for the given class, or create it if needed.
+  NSString* className = NSStringFromClass(item.cellClass);
+  MDCCollectionViewCell* cell = gSharedSizingCells[className];
+  if (!cell) {
+    cell = [[item.cellClass alloc] init];
+    // Don't use autoresizing mask constraints, as they will conflict when
+    // laying out the cell.
+    cell.contentView.translatesAutoresizingMaskIntoConstraints = NO;
+    // Store it in the dictionary.
+    gSharedSizingCells[className] = cell;
+  }
+
+  // Configure the cell with the item.
+  [item configureCell:cell];
+  return [cell cr_preferredHeightForWidth:targetWidth];
+}
+
+- (CGFloat)cr_preferredHeightForWidth:(CGFloat)targetWidth {
+  // Set the cell's frame to use the target width.
+  CGRect frame = self.frame;
+  const CGFloat kMaxHeight = 0;
+  frame.size = CGSizeMake(targetWidth, kMaxHeight);
+  self.frame = frame;
+
+  // Layout the cell.
+  [self setNeedsLayout];
+  [self layoutIfNeeded];
+
+  // Compute how tall the cell needs to be.
+  CGSize computedSize =
+      [self systemLayoutSizeFittingSize:UILayoutFittingCompressedSize];
+
+  return computedSize.height;
+}
+
+@end