Use reference cells for measurement.

// FREEBIE

Signal/src/views/OWSSystemMessageCell.m

@@ -261,10 +261,7 @@ NS_ASSUME_NONNULL_BEGIN
     result.height += self.topVMargin;
     result.height += self.bottomVMargin;
 
-    self.titleLabel.font = [self titleFont];
     [self applyTitleForInteraction:interaction label:self.titleLabel];
-    self.titleLabel.numberOfLines = 0;
-    self.titleLabel.lineBreakMode = NSLineBreakByWordWrapping;
     CGFloat maxTitleWidth = (collectionViewWidth - ([self hMargin] * 2.f + [self hSpacing] + [self iconSize]));
     CGSize titleSize = [self.titleLabel sizeThatFits:CGSizeMake(maxTitleWidth, CGFLOAT_MAX)];
     CGFloat contentHeight = ceil(MAX([self iconSize], titleSize.height));

Signal/src/views/OWSUnreadIndicatorCell.m

@@ -75,13 +75,11 @@ NS_ASSUME_NONNULL_BEGIN
     [self.bannerView addSubview:self.bannerBottomHighlightView2];
 
     self.titleLabel = [UILabel new];
-    self.titleLabel.text = [self titleForInteraction:self.interaction];
     self.titleLabel.textColor = [UIColor colorWithRGBHex:0x403e3b];
     self.titleLabel.font = [self titleFont];
     [self.bannerView addSubview:self.titleLabel];
 
     self.subtitleLabel = [UILabel new];
-    self.subtitleLabel.text = [self subtitleForInteraction:self.interaction];
     self.subtitleLabel.textColor = [UIColor ows_infoMessageBorderColor];
     self.subtitleLabel.font = [self subtitleFont];
     self.subtitleLabel.numberOfLines = 0;
@@ -101,6 +99,9 @@ NS_ASSUME_NONNULL_BEGIN
 
     _interaction = interaction;
 
+    self.titleLabel.text = [self titleForInteraction:self.interaction];
+    self.subtitleLabel.text = [self subtitleForInteraction:self.interaction];
+
     self.backgroundColor = [UIColor whiteColor];
 
     [self setNeedsLayout];
@@ -225,6 +226,7 @@ NS_ASSUME_NONNULL_BEGIN
     UILabel *label = self.titleLabel;
     label.font = [self titleFont];
     label.text = title;
+    label.numberOfLines = 1;
     result.height += ceil([label sizeThatFits:CGSizeZero].height);
 
     if (subtitle.length > 0) {