Tested the issue in Android and able to reproduce the issue. 

Steps Followed:
1. Launched chrome , changed text scaling to 110% from accessibility section of Google chrome settings
2. Navigated to reddit.com/r/chrome

Chrome versions tested:
70.0.3512.0(Latest canary)

OS:
Android 9.0.0

Android Devices:
Pixel XL

Using the per-revision bisect providing the bisect results,
Good Build - 70.0.3508.0
Bad Build - 70.0.3509.0

CL: https://chromium.googlesource.com/chromium/src/+/d0b8bbd2dbf9c06dcbbd01a4b1285cf7a1bc2ba0

@ eirage: Could you please look into the issue, pardon me if it has nothing to do with your changes and if possible please assign it to owner concerned. Adding RB-Stable as this is a recent regression. Please remove if this is not the case.

Please navigate to below link for log's  --
go/chrome-androidlogs/871054

Thanks!

I did a little more testing and yes, this only happens when zoom for DSF is enabled

Thanks a lot for providing the reproduce procedure and digging for this. Yes I confirm this is cause by enabling zoom for dsf. 

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f5b24fda00d9389dfccb24dcc196ae0664b50d98

commit f5b24fda00d9389dfccb24dcc196ae0664b50d98
Author: Ella Ge <eirage@chromium.org>
Date: Sat Aug 11 16:12:28 2018

Fix text autosizer line height with zoomed

TextAutosizer::ComputeAutosizedFontSize are used in both font_builder and
computed_style. The size passed in from font_builder is computedsize,
which has zoom factor applied. But in ComputedStyle::SetTextAutosizingMultiplier,
zoom factor doesn't.
And also, kPleasantSize is hard-coded css pixel (without zoom factor), and it
was used in calculation with computed_size(with zoom factor).
The inconsistancy causes line height incorrect when multiplier applied(crbug/871124),
and also text sometime lost scaling(crbug/871054)

This CL correct the variable in ComputeAutosizedFontSize to computed_size,
and pass in effective_zoom, so the sizes are computed in correct scale.


Bug:  871054 , 871124
Change-Id: Icf546795663b76af3cd03e4e42da96483eb83af7
Reviewed-on: https://chromium-review.googlesource.com/1169972
Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582447}
[add] https://crrev.com/f5b24fda00d9389dfccb24dcc196ae0664b50d98/third_party/WebKit/LayoutTests/fast/text-autosizing/nested-em-line-height-zoomed-expected.html
[add] https://crrev.com/f5b24fda00d9389dfccb24dcc196ae0664b50d98/third_party/WebKit/LayoutTests/fast/text-autosizing/nested-em-line-height-zoomed.html
[modify] https://crrev.com/f5b24fda00d9389dfccb24dcc196ae0664b50d98/third_party/blink/renderer/core/css/resolver/font_builder.cc
[modify] https://crrev.com/f5b24fda00d9389dfccb24dcc196ae0664b50d98/third_party/blink/renderer/core/layout/text_autosizer.cc
[modify] https://crrev.com/f5b24fda00d9389dfccb24dcc196ae0664b50d98/third_party/blink/renderer/core/layout/text_autosizer.h
[modify] https://crrev.com/f5b24fda00d9389dfccb24dcc196ae0664b50d98/third_party/blink/renderer/core/style/computed_style.cc

Issue is verified on 70.0.3522.0

I found a reliable repro for a text scaling bug that isn't caused by zoom for DSF, please take a look 
https://bugs.chromium.org/p/chromium/issues/detail?id=874631