[ios] Fix height issue when TableViewUrlCell doesn't have title or host.

- Require minimum height equal the height of the favicon for the vertical stackview in TableViewUrlCell
- If title and host aren't available, use full url spec.

Screenshot: https://drive.google.com/file/d/1C19zooJG80phfS6gDiCnMZQa2NZJd9zA/view?usp=sharing

Bug: 878833
Change-Id: I11e91f583f014f88a208478bef767cb70972ce7b
Reviewed-on: https://chromium-review.googlesource.com/1235319
Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
Reviewed-by: Sergio Collazos <sczs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593303}

ios/chrome/browser/ui/table_view/cells/table_view_url_item.mm

@@ -88,8 +88,14 @@ const char kDefaultSupplementalURLTextDelimiter[] = "•";
 
 // Returns the text to use when configuring a TableViewURLCell's title label.
 - (NSString*)titleLabelText {
-  return self.title.length ? self.title
-                           : base::SysUTF8ToNSString(self.URL.host());
+  if (self.title.length) {
+    return self.title;
+  } else if (base::SysUTF8ToNSString(self.URL.host()).length) {
+    return base::SysUTF8ToNSString(self.URL.host());
+  } else {
+    // Backup in case host returns nothing (e.g. about:blank).
+    return base::SysUTF8ToNSString(self.URL.spec());
+  }
 }
 
 // Returns the text to use when configuring a TableViewURLCell's URL label.