This callback is only used in very limited ways, so just require that the
caller passes in the canonical supports pointer plus the participant.
This probably won't affect performance much.
Microtasks, resolved Promises and Observers are handled after the sync
task that caused them, in the order they were generated.
Also simplifies reentrancy handling.
Based-on: m-c 1193394
Based on Mozilla bug 1345177.
Changes from the original bug's patch:
- We don't have JS::CurrentThreadIsHeapCollecting, so let's use
trc->runtime()->isHeapCollecting() instead.
- Mozilla bug 1337117 renamed runtimeFromMainThread to
runtimeFromActiveCooperatingThread for Firefox 54, so let's use the former
This allows us to use a greater rendering depth for exceedingly-deep DOM trees
in layout, better matching what mainstream browsers are capable of. Note that
for 32-bit Windows the stack size MUST be set to larger than the default or Bad
Things Will Happen™ - we use 1.5 MB for this as a carefully-tuned value.
This needs to be capped specifically for JS use because some JavaScript
obfuscators deliberately trigger stack overflows and would lock up the browser
otherwise as long as there's still stack space to abuse. For web compatibility
we therefore limit this to 2MB in JS only (3x for ASAN) while still allowing
a greater depth for the layout engine.
This should be the last code backout for this. merging this branch
should get us back to the way we were (+ additional code changes for
later changes) as fasr as the unused unboxed code is concerned.
This creates a number of stubs and leaves some surrounding code that may be irrelevant (eg. recorded time stamps, status variables).
Stub resolution/removal should be a follow-up to this.
