Bisect Info:
===========
Good build : 53.0.2756.0,   Revision Range - 397359
Bad build  : 53.0.2757.0,   Revision Range - 397573

After executing the old bisect script , i got the following CL's between good and bad build versions
===========================================
https://chromium.googlesource.com/chromium/src/+log/47379284a4a83df80f1f539e87a069164c558d2e..775ae9da9a7371d726f634c9d0333b530b1b1b16

The suspecting Change Log is :
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https://chromium.googlesource.com/chromium/src/+/d326605487da452867181c1fe0dc7c6580b0d714

Review URL: https://codereview.chromium.org/1967913002

michaelpg@- Could you please look into this issue, if it's related to your change?  if not could you please help us to reassign this issue to the right owner.

to the font settings guy!

The "problem" is that the default minimum font size seems to be 0, so the text isn't hidden... just 0-size.

Dave, is 0 supposed to be the default minimum font size? It's odd that you can't set the setting back to 0 once you start using the slider.

That sounds like an initialization problem (either in the pref or in the UI).

Source? (0 seems like a perfectly valid minimum font size. I think a higher minimum font size, like "89px", makes WebKit render "font-size: 0px" as "font-size: 8px".)

#4, I don't think I follow. 

Setting the font size to zero causes the text to not render. I'm trying to imagine the case were a user would desire that (here I'm interjecting my opinion, I understand). 

The old options doesn't appear to provide a way to set the minimum font size to zero; it's reasonable that the new settings should behave similarly.

Here's a source for zero font size means don't render:
https://cs.chromium.org/chromium/src/third_party/WebKit/LayoutTests/fast/text/zero-font-size.html?type=cs&q=%22font+size%22+zero&l=5

To me that implies: that zero size fonts should not render; and that a zero sized font should not be automatically be promoted to a different font size.

#4, if the intent was that having an unset minimum_font_size *preference* is perfectly valid, then I agree with that. E.g. the preference may be unset (zero) and valid font size should be used instead. Sorry if I misunderstood the intent on comment #4. I do think that a using a font size of zero (not the pref) is incorrect here. The fix will allow for a pref of zero, but use a non-zero font size style even when the pref is unset (zero).

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/fd0523d1fb0087eb86205242d06a8044a5107ceb

commit fd0523d1fb0087eb86205242d06a8044a5107ceb
Author: dschuyler <dschuyler@chromium.org>
Date: Wed Mar 15 00:40:58 2017

[MD settings] set pref to valid slider value

This CL will move the minimum font size to the start of the range if the pref has not been changed (instead of using a font size of zero).

BUG= 692985 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2738333004
Cr-Commit-Position: refs/heads/master@{#456919}

[modify] https://crrev.com/fd0523d1fb0087eb86205242d06a8044a5107ceb/chrome/browser/resources/settings/appearance_page/appearance_fonts_page.html
[modify] https://crrev.com/fd0523d1fb0087eb86205242d06a8044a5107ceb/chrome/browser/resources/settings/appearance_page/appearance_fonts_page.js