Adding mediator for Sign-in promo

ios/chrome/browser/ui/authentication/signin_promo_item.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.
+
+#import "ios/chrome/browser/ui/authentication/signin_promo_item.h"
+
+#import "ios/chrome/browser/ui/authentication/signin_promo_view.h"
+#import "ios/chrome/browser/ui/uikit_ui_util.h"
+#include "ios/chrome/grit/ios_chromium_strings.h"
+#include "ui/base/l10n/l10n_util.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+@implementation SigninPromoItem
+
+@synthesize configurator = _configurator;
+
+- (instancetype)initWithType:(NSInteger)type
+                configurator:(id<SigninPromoViewConfigurator>)configurator {
+  self = [super initWithType:type];
+  if (self) {
+    self.cellClass = [SigninPromoCell class];
+    _configurator = configurator;
+  }
+  return self;
+}
+
+#pragma mark - CollectionViewItem
+
+- (void)configureCell:(SigninPromoCell*)cell {
+  [super configureCell:cell];
+  cell.signinPromoView.textLabel.text =
+      l10n_util::GetNSString(IDS_IOS_SIGNIN_PROMO_SETTINGS);

[lpromero, 2017/03/27 13:14:46]

Since this is not settable by items clients, I suggest moving it to the cell
directly, when creating the signInPromoView.

[jlebel, 2017/03/27 21:34:42]

The issue is then the item will not be usable for bookmark? 

+  [_configurator configureSigninPromoView:cell.signinPromoView];
+}
+
+@end
+
+@implementation SigninPromoCell
+
+@synthesize signinPromoView = _signinPromoView;
+
+- (instancetype)initWithFrame:(CGRect)frame {
+  self = [super initWithFrame:frame];
+  if (self) {
+    UIView* contentView = self.contentView;
+    _signinPromoView = [[SigninPromoView alloc] initWithFrame:self.bounds];

[lpromero, 2017/03/27 13:14:46]

Nit: I prefer to let the creator of the view set the
translatesAutorisizingMasksIntoConstraints instead of the view itself. Can you
remove it from the view and add it here?

[jlebel, 2017/03/27 21:34:42]

Done.

+    [contentView addSubview:_signinPromoView];
+    AddSameSizeConstraint(_signinPromoView, contentView);
+  }
+  return self;
+}
+
+// Implements -layoutSubviews as per instructions in documentation for
+// +[MDCCollectionViewCell cr_preferredHeightForWidth:forItem:].
+- (void)layoutSubviews {
+  [super layoutSubviews];
+
+  // Adjust the text label preferredMaxLayoutWidth when the parent's width
+  // changes, for instance on screen rotation.
+  CGFloat parentWidth = CGRectGetWidth(self.bounds);
+  _signinPromoView.textLabel.preferredMaxLayoutWidth =
+      parentWidth - 2 * _signinPromoView.horizontalPadding;
+
+  // Re-layout with the new preferred width to allow the label to adjust its
+  // height.
+  [super layoutSubviews];
+}
+
+@end