The NTB's drawing routine recreates the outlines in a bezier, and then flips it horizontally. In RTL mode it omits the flip. But for some reason that causes it to end up a pixel lower and I can't figure that out. It looks like a correct horizontal flip transformation to me. :(

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4d41ddea3d47519db49f44b64cb9261a9382c943

commit 4d41ddea3d47519db49f44b64cb9261a9382c943
Author: Leonard Grey <lgrey@chromium.org>
Date: Wed Jul 12 17:39:52 2017

[Mac] Render new tab button shadow/bottom edge correctly in RTL

Bug:  693772 
Change-Id: Ib49f0324ae91ca4c2f44554fb3316d3c43c57417
Reviewed-on: https://chromium-review.googlesource.com/566896
Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Leonard Grey <lgrey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#486010}
[modify] https://crrev.com/4d41ddea3d47519db49f44b64cb9261a9382c943/chrome/browser/ui/cocoa/new_tab_button.mm

Could any one please provide us repro steps and expected screen shot to verify the issue from test team end.

Thanks,

Hi kavvaru@

To repro, launch Chrome from the command line with:
-NSForceRightToLeftWritingDirection YES -AppleTextDirection YES --force-ui-direction=rtl --enable-features=MacRTL

The button should look exactly like it does in left-to-right (default) mode, only mirrored from left to right. There shouldn't be any extraneous shadows or misdrawn elements.

 Issue 737509  has been merged into this issue.