[ios] Don't show day if time synced is today or yesterday in Recent Tabs

Removes the date for sync times that occur within the same calendar day. Replaces date with "Yesterday" for sync times that occur in the previous calendar day.

Screenshot: https://drive.google.com/open?id=1uFZHxOgHytaARm97MWONgekuymVxRBvJ, https://drive.google.com/open?id=1ZZr5HR___1y_CuQKcoNP-5Umd2Lz5K3n

Bug: 870043
Change-Id: Id6d4ecb424d5e709e66e48cd57d0c4add5683b1c
Reviewed-on: https://chromium-review.googlesource.com/1177891Reviewed-by: Sergio Collazos <sczs@chromium.org>
Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583871}

ios/chrome/app/strings/ios_strings.grd

@@ -939,6 +939,9 @@ locale.  The strings in this file are specific to iOS.
       <message name="IDS_IOS_OPEN_TABS_RECENTLY_SYNCED" desc="Relative time display for small time deltas, anything less than a minute [Length: 10em] [iOS only]">
         Seconds ago
       </message>
+      <message name="IDS_IOS_OPEN_TABS_SYNCED_YESTERDAY" desc="Relative time display for time deltas that cover yesterday [Length: 10em] [iOS only]">
+        Yesterday
+      </message>
       <message name="IDS_IOS_OPTIONS_ACCOUNTS_ADD_ACCOUNT_BUTTON" desc="The title of the Add account button on the accounts settings screen [iOS only] [30em]">
         Add Account…
       </message>

ios/chrome/browser/ui/recent_tabs/recent_tabs_table_view_controller.mm

@@ -90,9 +90,6 @@ int const kNumberOfSectionsBeforeSessions = 1;
 const CGFloat kEstimatedRowHeight = 56;
 // Separation space between sections.
 const CGFloat kSeparationSpaceBetweenSections = 9;
-// The UI displays relative time for up to this number of hours and then
-// switches to absolute values.
-const int kRelativeTimeMaxHours = 4;
 // Section index for recently closed tabs.
 const int kRecentlyClosedTabsSectionIndex = 0;
 
@@ -832,23 +829,35 @@ const int kRecentlyClosedTabsSectionIndex = 0;
 
   if (last_used_delta.InMicroseconds() < base::Time::kMicrosecondsPerMinute) {
     timeString = l10n_util::GetNSString(IDS_IOS_OPEN_TABS_RECENTLY_SYNCED);
-    // This will return something similar to "Seconds ago mm/dd/yy"
-    return [NSString stringWithFormat:@"%@ %@", timeString, dateString];
+    // This will return something similar to "Seconds ago"
+    return [NSString stringWithFormat:@"%@", timeString];
   }
 
-  if (last_used_delta.InHours() < kRelativeTimeMaxHours) {
+  NSDate* date = [NSDate dateWithTimeIntervalSince1970:time.ToTimeT()];
+  timeString =
+      [NSDateFormatter localizedStringFromDate:date
+                                     dateStyle:NSDateFormatterNoStyle
+                                     timeStyle:NSDateFormatterShortStyle];
+
+  NSInteger today = [[NSCalendar currentCalendar] component:NSCalendarUnitDay
+                                                   fromDate:[NSDate date]];
+  NSInteger dateDay =
+      [[NSCalendar currentCalendar] component:NSCalendarUnitDay fromDate:date];
+
+  if (today == dateDay) {
     timeString = base::SysUTF16ToNSString(
         ui::TimeFormat::Simple(ui::TimeFormat::FORMAT_ELAPSED,
                                ui::TimeFormat::LENGTH_SHORT, last_used_delta));
-    // This will return something similar to "1 min/hour ago mm/dd/yy"
+    // This will return something similar to "1 min/hour ago"
+    return [NSString stringWithFormat:@"%@", timeString];
+  }
+
+  if (today - dateDay == 1) {
+    dateString = l10n_util::GetNSString(IDS_IOS_OPEN_TABS_SYNCED_YESTERDAY);
+    // This will return something similar to "H:MM Yesterday"
     return [NSString stringWithFormat:@"%@ %@", timeString, dateString];
   }
 
-  NSDate* date = [NSDate dateWithTimeIntervalSince1970:time.ToTimeT()];
-  timeString =
-      [NSDateFormatter localizedStringFromDate:date
-                                     dateStyle:NSDateFormatterNoStyle
-                                     timeStyle:NSDateFormatterShortStyle];
   // This will return something similar to "H:MM mm/dd/yy"
   return [NSString stringWithFormat:@"%@ %@", timeString, dateString];
 }