STR:

• open the debugger against https://test-sources.glitch.me/
• select frame1.html source

AR:
Only one of the two inline <script> have its line "breakable". i.e. you can set a breakpoint.
The other inline <script> is ignored.

ER:
You can set breakpoints on all inline <script>

This is specific to iframe's HTML page and probably relates to this code:
https://searchfox.org/mozilla-central/rev/efc480f2188fb43c9cccdfd2eef79749a19c20a3/devtools/client/debugger/src/client/firefox/create.js#100,112
which will force spawning a new dedicated source object for each individual inline script.
Whereas we expect only one for the html pages.
We do it right for top level target's sources in this makeSourceId method.

The severity field is not set for this bug.
:bomsy, could you have a look please?

For more information, please visit auto_nag documentation.

While adding this new html page for breakable lines,
I revisit how we load same-url.sjs and use this iframe document instead.
This feel more natural than dynamically injecting a document-builder iframe.

Also I promote breakable lines and positions tests to become features tests.

And it looks like adding the iframe target slow things down for the quick open.
So I tuned the related assertion to avoid intermittents.

Last but not least, this patch highlights two limitations for iframe html debugging:

• only the first inline script is "breakable" (others are ignored)
• on reload, no content is displayed at all (this is new to me)

https://hg.mozilla.org/mozilla-central/rev/13242fc72d38
https://hg.mozilla.org/mozilla-central/rev/f6ddce73b688