Crash annotations in content processes are currently sent over IPC via
shared memory buffers. To pave the way for the Rust rewrite of the exception
handler we are removing this code and gathering all the crash annotations
within the content processes themselves. This patch causes annotations to be
stored in the global table of each content process. They are then streamed
out to the parent process by the exception handler together with the
exception-time annotations.
This has a number of benefits:
* we have one less channel to exchange data between content processes and
the parent process
* we save memory because we don't need to allocate the shared memory buffers
* annotations are faster because we don't stream them all out every time one
changes
* we won't truncate annotations anymore if we run out of space in the shared
segment.
* we don't need delayed annotations anymore, so we can get rid of the
associated machinery
As I refactored the code I tried to adjust all the obsolete comments,
consolidate shared code and remove the redundant steps that were sometimes
present. In many places we had two entire crash annotation tables we merged to
change just a couple; that comes from the fact that historically we loaded
them from disk. Now it doesn't matter anymore and we can just go ahead and
change the ones we care about.
Differential Revision: https://phabricator.services.mozilla.com/D62586
--HG--
extra : moz-landing-system : lando
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