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"
+
+#include "base/logging.h"
+#import "ios/chrome/browser/ui/authentication/signin_promo_view.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 signinPromoViewConfigurator = _signinPromoViewConfigurator;
+
+- (instancetype)initWithType:(NSInteger)type
+    signinPromoViewConfigurator:
+        (id<SigninPromoViewConfigurator>)signinPromoViewConfigurator {
+  self = [super initWithType:type];
+  if (self) {
+    self.cellClass = [SigninPromoCell class];
+    _signinPromoViewConfigurator = signinPromoViewConfigurator;
+  }
+  return self;
+}
+
+- (instancetype)initWithType:(NSInteger)type {
+  NOTREACHED();
+  return nil;
+}
+
+#pragma mark - CollectionViewItem
+
+- (void)configureCell:(SigninPromoCell*)cell {
+  [super configureCell:cell];
+  cell.signinPromoView.textLabel.text =
+      l10n_util::GetNSString(IDS_IOS_SIGNIN_PROMO_SETTINGS);
+  [_signinPromoViewConfigurator configureSigninPromoView:cell.signinPromoView];

[msarda, 2017/03/16 22:15:31]

Should the configuration also configure the textLabel of the cell's
signinPromoView?

[jlebel, 2017/03/21 17:22:28]

I can but this is a fixed value, and the value is not related to the data
related to the profile. This looks fine to me.

[msarda, 2017/03/22 12:18:38]

OK, I see (basically this is not something configurable, so there is nothing to
be configured here).

+}
+
+@end
+
+@implementation SigninPromoCell
+
+@synthesize signinPromoView = _signinPromoView;
+
+- (instancetype)initWithFrame:(CGRect)frame {
+  self = [super initWithFrame:frame];
+  if (self) {
+    [self addSubviews];
+  }
+  return self;
+}
+
+- (void)addSubviews {
+  UIView* contentView = self.contentView;
+
+  _signinPromoView = [[SigninPromoView alloc] initWithFrame:self.bounds];
+  [contentView addSubview:_signinPromoView];
+  [NSLayoutConstraint activateConstraints:@[
+    [_signinPromoView.topAnchor constraintEqualToAnchor:contentView.topAnchor],

[msarda, 2017/03/16 22:15:31]

Is the goal of these constraints to have the same size for _signinPromoView and
contentView? If so, then consider using:
Consider using function AddSameSizeConstraint (see
https://cs.chromium.org/chromium/src/ios/chrome/browser/ui/uikit_ui_util.mm?r...
).

[jlebel, 2017/03/21 17:22:28]

Done.

+    [_signinPromoView.bottomAnchor
+        constraintEqualToAnchor:contentView.bottomAnchor],
+    [_signinPromoView.leftAnchor
+        constraintEqualToAnchor:contentView.leftAnchor],
+    [_signinPromoView.rightAnchor
+        constraintEqualToAnchor:contentView.rightAnchor],
+  ]];
+}
+
+// Implements -layoutSubviews as per instructions in documentation for

[msarda, 2017/03/16 22:15:31]

I suppose this comment is not needed (but probably Louis knows better).

[jlebel, 2017/03/21 17:22:28]

I've done exactly the same implementation than those methods:
https://cs.chromium.org/search/?q=%22Implements+-layoutSubviews+as+per+instru...

So I'm guessing I need the same comment. But I don't mind removing it.

+// +[MDCCollectionViewCell cr_preferredHeightForWidth:forItem:].
+- (void)layoutSubviews {
+  [super layoutSubviews];

[msarda, 2017/03/16 22:15:31]

I think calling [super layoutSubviews]  here is unnecessary the following
reasons:
* the bounds of this SigninPromoCell will not change after this call
(self.bounds are the same whether [super layoutSubviews] is called or not)
* This means that the parentWidth is the same are the same whether [super
layoutSubviews] is called or not
* This means that _signinPromoView.textLabel.preferredMaxLayoutWidth is the same
whether [super layoutSubviews] is called or not

[jlebel, 2017/03/21 17:22:28]

-[MDCollectionViewCell layoutSubviews layoutSubviews] does exist (and
-[UICollectionViewCell layoutSubviews] too).
So I think it is a good idea to call it. The only gain would be speed
optimisation?

[msarda, 2017/03/22 12:18:38]

Ok, I've added a comment on the next patch. I'd like Louis's opinion about this
as well.

+
+  // 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