User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:73.0) Gecko/20100101 Firefox/73.0

Steps to reproduce:

I develop locally using webpack or brower-sync. Both tools trigger this issue.

While having the devtools open and working on a page's source code, the page gets automatically refreshed every time I save a file.

Actual results:

The RAM usage of Firefox increases continually, until all of my 16 GB RAM and 16 GB of swap are allocated.

Closing the devtools frees some of the memory. Closing the tab frees some more. Restarting the browser frees all of the allocated memory.

Expected results:

RAM usage should not increase while reloading a web page.

As a brief investigation, this is a profile with native allocation. Running react-starter-kit locally and repeatably editing/saving a CSS file with the Debugger open:

https://perfht.ml/37X9vaW

No obvious winners, but memoize of getCachedResource might be one part where Debugger retains memory.

Dupe of bug 1084605 maybe? The JS engine debugger stuff holds pages alive. Bug 1084626 is one possible fix, but it broke too many devtools tests to land.

Closing the devtools frees some of the memory

Related: https://bugzilla.mozilla.org/show_bug.cgi?id=1439509.

The priority flag is not set for this bug.
:pbro, could you have a look please?

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