This roll moves Juggler component registration to a new system that
is used in XPCOM: this is what both RemoteAgent and Marionette use.
Drive-by: we now have to explicitly pass default values to dispatched
mouse events to avoid a `MOZ_ASSERT` trigger inside a drag service
native code.
Manual conflict resolutions: ab3ed0cb2c
Patch by @dpino
Fixes the following error on Ubuntu 18:
```
[716/8153] Linking CXX shared library lib/libmbmalloc.so
FAILED: lib/libmbmalloc.so
: && <CXX> -fPIC -fdiagnostics-color=always -Wextra -Wall -pipe -Wno-odr -Wno-stringop-overflow -Wno-nonnull -Wno-array-bounds -Wno-expansion-to-defined -Wno-noexcept-type -Wno-psabi -Wno-misleading-indentation -Wno-maybe-uninitialized -Wwrite-strings -Wundef -Wpointer-ari>
/usr/bin/ld: Source/bmalloc/CMakeFiles/bmalloc.dir/libpas/src/libpas/pas_deallocate.c.o: relocation R_X86_64_PC32 against symbol `pas_segregated_page_deallocation_did_fail' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: Bad value
```
Pretty-diff: a479046919
* nsIScreencastServiceClient is not thread safe refcounted so we make nsScreencastService::Session a thread safe refcounted object and keep it alive while there are inflight frames. Once such frames get handled on the main thread we check if the session has been stopped.
* Removed mCaptureCallbackCs in favor of atomic counter (mClient is not accessed only on the main thread).
* HeadlessWindowCapturer now holds RefPtr to the headless window object to avoid use after free when clearing it as a listener on the widget.
* ScreencastEncoder is not ref counted anymore.
Pretty-diff: 5f5042ff1e
Turns out the weird compilation error is fixed if we use Clang 14
to compile.
This is the same clang that would've been shipped in mozilla build
toolchain.
The canonical script to install pip3 doesn't work with Python3.6
that is used to compile WebKit on Ubuntu 18.04, so we fallback
to installing pip3 from apt.
It was recently enabled by default upstream 461deb6c6d
We have this feature disabled in Chromium as we want the iframes to be eagerly loaded to avoid clients' confusion. This PR disables it back in WebKit too.
Pretty-diff: 7aad962e5d
Turns out we were bundling x86_64 `libstdc++` with aarch64
builds on Ubuntu, which was useless and implies that this
library might not be needed at all.
Ubuntu 18.04 ships Python 3.6 by default on Ubuntu18.04; this python,
however, fails to run Firefox build system, so we have to install
Python 3.8 and default it to `python3`.
Prebuilt WASI sysroot is not availabe any more, so this patch
disables sandboxing via WASI for now in our builds.
I tried compiling WASI manually, but it didn't work out for me
for some reason.
