[iOS] Support Dynamic Type for ReadingList empty string

This CL changes the string displayed when the ReadingList is empty so
it doesn't overflow below the bottom and top toolbar when the font is
too big. It does that by limiting the font size.

Bug: 893535
Cq-Include-Trybots: luci.chromium.try:ios-simulator-cronet;luci.chromium.try:ios-simulator-full-configs
Change-Id: I03335f2c1fee192a765b6e85011627c0f5ae2019
Reviewed-on: https://chromium-review.googlesource.com/c/1276925
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#599153}

ios/chrome/browser/ui/reading_list/empty_reading_list_message_util.mm

@@ -27,9 +27,30 @@ NSString* const kReadLaterTextMarker = @"READ_LATER_TEXT";
 // Background view constants.
 const CGFloat kLineSpacing = 4;
 
+UIFont* FontWithMaximumForCategory(UIContentSizeCategory category,
+                                   UIFontTextStyle font_style) {
+  if (ContentSizeCategoryIsAccessibilityCategory(category)) {
+    return [UIFont
+            preferredFontForTextStyle:font_style
+        compatibleWithTraitCollection:
+            [UITraitCollection traitCollectionWithPreferredContentSizeCategory:
+                                   UIContentSizeCategoryAccessibilityLarge]];
+  }
+  return [UIFont preferredFontForTextStyle:font_style];
+}
+
 // Returns the font to use for the message text.
 UIFont* GetMessageFont() {
-  return [UIFont preferredFontForTextStyle:UIFontTextStyleBody];
+  return FontWithMaximumForCategory(
+      [UIApplication sharedApplication].preferredContentSizeCategory,
+      UIFontTextStyleBody);
+}
+
+// Returns the font to use for the message text.
+UIFont* GetInstructionFont() {
+  return FontWithMaximumForCategory(
+      [UIApplication sharedApplication].preferredContentSizeCategory,
+      UIFontTextStyleHeadline);
 }
 
 // Returns the attributes to use for the message text.
@@ -54,8 +75,7 @@ NSMutableDictionary* GetMessageAttributes() {
 // Later" option.
 NSMutableDictionary* GetInstructionAttributes() {
   NSMutableDictionary* attributes = GetMessageAttributes();
-  attributes[NSFontAttributeName] =
-      [UIFont preferredFontForTextStyle:UIFontTextStyleHeadline];
+  attributes[NSFontAttributeName] = GetInstructionFont();
   return attributes;
 }
 

ios/chrome/browser/ui/reading_list/reading_list_table_view_controller.mm

@@ -22,6 +22,7 @@
 #import "ios/chrome/browser/ui/reading_list/reading_list_toolbar_button_commands.h"
 #import "ios/chrome/browser/ui/reading_list/reading_list_toolbar_button_manager.h"
 #import "ios/chrome/browser/ui/table_view/cells/table_view_text_header_footer_item.h"
+#import "ios/chrome/browser/ui/uikit_ui_util.h"
 #include "ios/chrome/grit/ios_strings.h"
 #include "ui/base/l10n/l10n_util_mac.h"
 
@@ -224,6 +225,15 @@ ReadingListSelectionState GetSelectionStateForSelectedCounts(
     [self exitEditingModeAnimated:YES];
 }
 
+- (void)traitCollectionDidChange:(UITraitCollection*)previousTraitCollection {
+  [super traitCollectionDidChange:previousTraitCollection];
+  if (!self.dataSource.hasElements &&
+      self.traitCollection.preferredContentSizeCategory !=
+          previousTraitCollection.preferredContentSizeCategory) {
+    [self tableIsEmpty];
+  }
+}
+
 #pragma mark - UITableViewDataSource
 
 - (void)tableView:(UITableView*)tableView