To clarify - you are using the workspace feature, right? You map a CSS URL that your page references to a file on your device and then follow those steps, right?

Correct, files are on localhost.  If you also have the file open on a text editor it refreshes and is empty.  That doesn't affect the problem, just saying it for sure does empty the file. 

Update: Change:

I just experienced this bug with all changes saved now.  But it had one different twist.  The CSS file was only cleared in memory.  It remained intact on my HDD.  I was able to recover the CSS code with a separate text editor.  I.E. hitting F5(refresh) pulled in the correct, up to date, CSS file.

Hi Trendal!

The "main window" in your description is a sources Panel CSS file?

That is correct.  I'm sorry I'm not familiar with the terms here.  I've used the Dev Tools for years but I've been blind to a lot of it's abilities.

So to clarify, the bug has not manifested itself while editing code in the Sources panel, actually.  It crashes when the Elements panel is in use, and you are incrementing or decrementing a value in the live Style's tab on the right pane with the up/down arrow on the keyboard.

I've attached a file pointing to the area I'm talking about.

The issue is fairly consistent as in it does it most everytime I use that feature.  But it varies in length of time holding the arrow key to make it happen.

My attachment isn't appearing, is there something limiting me from attaching an image file?

You should be able to attach... There might be some outage.
In the meantime, perhaps share it using Google Drive or something. :(

https://www.dropbox.com/s/jslq5w7yrp4niy6/dev%20tools%20bug.png?dl=0

That is just showing WHERE the problem occurs.  I suspect it won't do anything on that page as it's just the Google home page in the browser, not a mapped file on the hard drive. 

I have another issue arising that may put light on the current problem.

I have my whole web app directory mapped in dev tools.  I only use the editing feature for CSS.  I code Javascript etc in a separate text editor.  A couple times a day, my separate text editor is warning me that the file was edited somewhere else.  This was not happening before.  There are no edits that I can find, but I feel like the dev tools is somehow tweaking the file enough to trigger this warning.

Thanks Trendal for all the input. I think I might have clues on what's going on regarding the CSS situation.

It's still unclear who/why triggers the write of your JS files. Do you switch branches in git or something like that?

I'm using git but I don't think it's related.  I'm not doing anything with git, haven't pushed, pulled, commited, etc.  I can't say for certain if it coincidences or not but I get an error in the Dev Tools console about the Live Edit failing when I am saving Javascript code in my text editor sometimes.

I've closed everything, restarted the computer, made for positive I don't have the file open anywhere else, read or write mode, and it continues to do it.  The only place that file is open in is gedit and Dev Tools.  I can't seem to find any consistent trigger for this error although I don't believe it happens if I don't have that JS file open in the Sources tab.

Okay, I just got the notice in Dev Tools that the CSS file I'm actively working with just changed somewhere else.  So I'm not sure what that means.  I don't have the file open in any other editor, it's in a git directory, but not in any other synchronization system, like Dropbox etc.

As far as I know that file is only being edited inside Dev Tools.  I tried yesterday to use auditctl to watch that file for changes but I failed.  I don't know enough about auditctl yet.

If someone can point me to some automated monitoring I could setup to troubleshoot this, I'd be happy to try it.

Started: https://codereview.chromium.org/2702583003/

This should never happen to you again after the patch lands.

Sweet, thanks.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/200c7f1b24cac1345bfed596d5ba961bc993c63a

commit 200c7f1b24cac1345bfed596d5ba961bc993c63a
Author: lushnikov <lushnikov@chromium.org>
Date: Sat Feb 18 06:15:33 2017

DevTools: do not assign empty content to CSS UISourceCode in case of protocol error

This patch removes an outdated logic which was assigning empty content
to CSS UISourceCodes in case of protocol error.

BUG= 687360 
R=dgozman

Review-Url: https://codereview.chromium.org/2702583003
Cr-Commit-Position: refs/heads/master@{#451423}

[add] https://crrev.com/200c7f1b24cac1345bfed596d5ba961bc993c63a/third_party/WebKit/LayoutTests/http/tests/inspector/persistence/persistence-do-not-overwrite-css-expected.txt
[add] https://crrev.com/200c7f1b24cac1345bfed596d5ba961bc993c63a/third_party/WebKit/LayoutTests/http/tests/inspector/persistence/persistence-do-not-overwrite-css.html
[modify] https://crrev.com/200c7f1b24cac1345bfed596d5ba961bc993c63a/third_party/WebKit/Source/devtools/front_end/bindings/StylesSourceMapping.js
[modify] https://crrev.com/200c7f1b24cac1345bfed596d5ba961bc993c63a/third_party/WebKit/Source/devtools/front_end/common/StaticContentProvider.js
[modify] https://crrev.com/200c7f1b24cac1345bfed596d5ba961bc993c63a/third_party/WebKit/Source/devtools/front_end/sdk/CSSModel.js
[modify] https://crrev.com/200c7f1b24cac1345bfed596d5ba961bc993c63a/third_party/WebKit/Source/devtools/front_end/sdk/CSSStyleSheetHeader.js

The patch should hit Canary today or tomorrow; please, give it a try after that. If the issue happens again, feel free to either write here or file another bug!