This happens with WebKitGTK 2.24.1 and (at least) the Japanese locale using the fonts-noto-cjk package.
In order to reproduce it you just need to open any plain text file using the Japanese locale, e.g:
LC_ALL=ja_JP.UTF-8 MiniBrowser file:///etc/profile
The white space does not appear at all. Using a different locale (I tried C and es_ES.UTF-8) it work fine.
This is causing problems displaying e-mail in Evolution. See Debian bugs https://bugs.debian.org/926872 and https://bugs.debian.org/928399
Created attachment 369368 [details]
(In reply to Carlos Garcia Campos from comment #1)
> Created attachment 369368 [details]
This patch fixes the issue for me.
Comment on attachment 369368 [details]
Attachment 369368 [details] did not pass win-ews (win):
New failing tests:
Created attachment 369373 [details]
Archive of layout-test-results from ews211 for win-future
The attached test failures were seen while running run-webkit-tests on the win-ews.
Bot: ews211 Port: win-future Platform: CYGWIN_NT-10.0-17763-3.0.5-338.x86_64-x86_64-64bit
*** Bug 197570 has been marked as a duplicate of this bug. ***
Committed r245094: <https://trac.webkit.org/changeset/245094>