This doesn't seem as important as other bugs; dropping to P3 unless you object. 

We should do this for all cells that allow user input*

Thanks for helping out, Rohit!

To explain further, whenever we select a textfield for editing the textcolor should change from lightGray to black.

https://chromium-review.googlesource.com/c/chromium/src/+/1186701

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/764f185025c76b7ff3b2ef9727db47946488efac

commit 764f185025c76b7ff3b2ef9727db47946488efac
Author: Rohit Rao <rohitrao@chromium.org>
Date: Fri Aug 24 12:20:29 2018

[ios] Change text color to black when editing bookmarks fields.

BUG= 855320 

Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I4fb596298e417795877400a94fc7d80349c80673
Reviewed-on: https://chromium-review.googlesource.com/1186701
Reviewed-by: Sergio Collazos <sczs@chromium.org>
Commit-Queue: Rohit Rao <rohitrao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585804}
[modify] https://crrev.com/764f185025c76b7ff3b2ef9727db47946488efac/ios/chrome/browser/ui/bookmarks/bookmark_edit_view_controller.mm
[modify] https://crrev.com/764f185025c76b7ff3b2ef9727db47946488efac/ios/chrome/browser/ui/bookmarks/bookmark_folder_editor_view_controller.mm
[modify] https://crrev.com/764f185025c76b7ff3b2ef9727db47946488efac/ios/chrome/browser/ui/bookmarks/cells/bookmark_text_field_item.h
[modify] https://crrev.com/764f185025c76b7ff3b2ef9727db47946488efac/ios/chrome/browser/ui/bookmarks/cells/bookmark_text_field_item.mm

Verified on chrome beta version 70.0.3538.47 on iPhone 6s plus with iOS 12 beta 2, iPad 2018 with iOS 11.4.1.  When the cursor is placed in text box, the color of text is changed from light gray to black. Looks good.