Pivot now supports RemoteAccessible. However, the XPCOM implementation and the tests only support LocalAccessible. The XPCOM implementation also doesn't match how Pivot is used by platform code; e.g. it maintains state, there is a virtual cursor on the DocAccessible, etc.

We need to reimagine the XPCOM interface and the tests accordingly. We should also remove mVirtualCursor from DocAccessible.

We probably also want to remove AccVCChangeEvent.

This wasn't needed to get Android working. We should still do it so things are cleaner, though.

This patch does several things:

1. Remove virtual cursor doc accessible member.
2. Remove state-keeping nsAccessiblePivot implementation and replace it
   with something that is much more similar to the native Pivot
   interface.
3. Move nsIAccessiblePivot implementation to xpcom and rename it
   xpcAccessiblePivot.
4. Delete mochitests and introduce browser tests.
5. Make new xpcom implementation work on remote accessibles as well.

Backed out for causing Bp-nu bustages in xpcAccessiblePivot.h.

• Backout link
• Push with failures
• Failure Log
• Failure line: /builds/worker/checkouts/gecko/accessible/xpcom/xpcAccessiblePivot.h:35:3: error: unknown type name 'Accessible'; did you mean 'mozilla::a11y::Accessible'?

There are also some gv-junit failures, as it can be seen here.

Backed out for causing bustages at LocalAccessible.

Backout link: https://hg.mozilla.org/integration/autoland/rev/87e6c40a962924daad35a788c3dbfbfdba9003d1

Push with failures: https://treeherder.mozilla.org/jobs?repo=autoland&resultStatus=testfailed%2Cbusted%2Cexception%2Cretry%2Cusercancel&revision=4d92a76cedd014a3427e33859e681fa8ef10b88b&selectedTaskRun=cNHnt-nMSU-WeqV7cBYDtg.0

Failure log: https://treeherder.mozilla.org/logviewer?job_id=420724771&repo=autoland&lineNumber=105144

Backed out for causing build bustages on DocAccessibleWrap.

• Push with failures

• Failure log

• Backout link

[task 2023-06-27T23:38:38.941Z] 23:38:38     INFO -  gmake[4]: Entering directory '/builds/worker/workspace/obj-build/accessible/mac'
[task 2023-06-27T23:38:38.941Z] 23:38:38     INFO -  accessible/mac/DocAccessibleWrap.o
[task 2023-06-27T23:38:38.944Z] 23:38:38     INFO -  /builds/worker/fetches/sccache/sccache /builds/worker/fetches/clang/bin/clang++ -isysroot /builds/worker/fetches/MacOSX13.3.sdk -mmacosx-version-min=10.12 -stdlib=libc++ --target=x86_64-apple-darwin -o DocAccessibleWrap.o -c  -I/builds/worker/workspace/obj-build/dist/stl_wrappers -fvisibility=hidden -fvisibility-inlines-hidden -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fstack-protector-strong -DNDEBUG=1 -DTRIMMED=1 -DMOZ_HAS_MOZGLUE -DMOZILLA_INTERNAL_API -DIMPL_LIBXUL -DSTATIC_EXPORTABLE_JS_API -I/builds/worker/checkouts/gecko/accessible/mac -I/builds/worker/workspace/obj-build/accessible/mac -I/builds/worker/checkouts/gecko/accessible/base -I/builds/worker/checkouts/gecko/accessible/generic -I/builds/worker/checkouts/gecko/accessible/html -I/builds/worker/checkouts/gecko/accessible/ipc -I/builds/worker/checkouts/gecko/accessible/xul -I/builds/worker/checkouts/gecko/layout/generic -I/builds/worker/checkouts/gecko/layout/xul -I/builds/worker/checkouts/gecko/widget -I/builds/worker/checkouts/gecko/widget/cocoa -I/builds/worker/workspace/obj-build/ipc/ipdl/_ipdlheaders -I/builds/worker/checkouts/gecko/ipc/chromium/src -I/builds/worker/workspace/obj-build/dist/include -I/builds/worker/workspace/obj-build/dist/include/nspr -I/builds/worker/workspace/obj-build/dist/include/nss -DMOZILLA_CLIENT -include /builds/worker/workspace/obj-build/mozilla-config.h -fno-sized-deallocation -fno-aligned-new -fcrash-diagnostics-dir=/builds/worker/artifacts -fno-exceptions -fPIC -fno-rtti -ffunction-sections -fdata-sections -fno-exceptions -fno-math-errno -pipe -gdwarf-4 -Xclang -load -Xclang /builds/worker/workspace/obj-build/build/clang-plugin/libclang-plugin.so -Xclang -add-plugin -Xclang moz-check -O3 -fno-omit-frame-pointer -funwind-tables -Werror -Wall -Wbitfield-enum-conversion -Wdeprecated-this-capture -Wempty-body -Wformat-type-confusion -Wignored-qualifiers -Wpointer-arith -Wshadow-field-in-constructor-modified -Wsign-compare -Wtautological-constant-in-range-compare -Wtype-limits -Wno-error=tautological-type-limit-compare -Wunreachable-code -Wunreachable-code-return -Wunused-but-set-parameter -Wno-invalid-offsetof -Wclass-varargs -Wempty-init-stmt -Wfloat-overflow-conversion -Wfloat-zero-conversion -Wloop-analysis -Wno-range-loop-analysis -Wc++2a-compat -Wenum-compare-conditional -Wenum-float-conversion -Wno-error=deprecated -Wno-error=deprecated-anon-enum-enum-conversion -Wno-error=deprecated-enum-enum-conversion -Wno-error=deprecated-pragma -Wno-error=deprecated-this-capture -Wcomma -Wimplicit-fallthrough -Wduplicate-method-arg -Wduplicate-method-match -Wmissing-method-return-type -Wobjc-signed-char-bool -Wsemicolon-before-method-body -Wsuper-class-method-mismatch -Wstring-conversion -Wno-inline-new-delete -Wno-error=deprecated-declarations -Wno-error=array-bounds -Wno-error=free-nonheap-object -Wno-error=atomic-alignment -Wno-error=deprecated-builtins -Wformat -Wformat-security -Wno-psabi -Wthread-safety -Werror=unguarded-availability-new -Wno-error=builtin-macro-redefined -Wno-unknown-warning-option -fno-strict-aliasing -ffp-contract=off  -MD -MP -MF .deps/DocAccessibleWrap.o.pp   -x objective-c++ -fobjc-exceptions   /builds/worker/checkouts/gecko/accessible/mac/DocAccessibleWrap.mm
[task 2023-06-27T23:38:38.946Z] 23:38:38    ERROR -  /builds/worker/checkouts/gecko/accessible/mac/DocAccessibleWrap.mm:64:22: error: member access into incomplete type 'const nsRoleMapEntry'
[task 2023-06-27T23:38:38.946Z] 23:38:38     INFO -            if (roleMap->liveAttRule == ePoliteLiveAttr ||
[task 2023-06-27T23:38:38.946Z] 23:38:38     INFO -                       ^
[task 2023-06-27T23:38:38.946Z] 23:38:38     INFO -  /builds/worker/workspace/obj-build/dist/include/mozilla/a11y/Accessible.h:18:8: note: forward declaration of 'nsRoleMapEntry'
[task 2023-06-27T23:38:38.946Z] 23:38:38     INFO -  struct nsRoleMapEntry;
[task 2023-06-27T23:38:38.946Z] 23:38:38     INFO -         ^
[task 2023-06-27T23:38:38.946Z] 23:38:38    ERROR -  /builds/worker/checkouts/gecko/accessible/mac/DocAccessibleWrap.mm:65:22: error: member access into incomplete type 'const nsRoleMapEntry'
[task 2023-06-27T23:38:38.946Z] 23:38:38     INFO -                roleMap->liveAttRule == eAssertiveLiveAttr) {
[task 2023-06-27T23:38:38.946Z] 23:38:38     INFO -                       ^
[task 2023-06-27T23:38:38.946Z] 23:38:38     INFO -  /builds/worker/workspace/obj-build/dist/include/mozilla/a11y/Accessible.h:18:8: note: forward declaration of 'nsRoleMapEntry'
[task 2023-06-27T23:38:38.946Z] 23:38:38     INFO -  struct nsRoleMapEntry;
[task 2023-06-27T23:38:38.946Z] 23:38:38     INFO -         ^
[task 2023-06-27T23:38:38.946Z] 23:38:38    ERROR -  /builds/worker/checkouts/gecko/accessible/mac/DocAccessibleWrap.mm:64:39: error: use of undeclared identifier 'ePoliteLiveAttr'
[task 2023-06-27T23:38:38.946Z] 23:38:38     INFO -            if (roleMap->liveAttRule == ePoliteLiveAttr ||
[task 2023-06-27T23:38:38.946Z] 23:38:38     INFO -                                        ^
[task 2023-06-27T23:38:38.946Z] 23:38:38    ERROR -  /builds/worker/checkouts/gecko/accessible/mac/DocAccessibleWrap.mm:65:39: error: use of undeclared identifier 'eAssertiveLiveAttr'
[task 2023-06-27T23:38:38.946Z] 23:38:38     INFO -                roleMap->liveAttRule == eAssertiveLiveAttr) {
[task 2023-06-27T23:38:38.946Z] 23:38:38     INFO -                                        ^
[task 2023-06-27T23:38:38.946Z] 23:38:38     INFO -  4 errors generated.
[task 2023-06-27T23:38:38.946Z] 23:38:38    ERROR -  gmake[4]: *** [/builds/worker/checkouts/gecko/config/rules.mk:675: DocAccessibleWrap.o] Error 1
[task 2023-06-27T23:38:38.946Z] 23:38:38     INFO -  gmake[4]: Leaving directory '/builds/worker/workspace/obj-build/accessible/mac'
[task 2023-06-27T23:38:38.946Z] 23:38:38     INFO -  gmake[4]: Target 'target-objects' not remade because of errors.
[task 2023-06-27T23:38:38.946Z] 23:38:38    ERROR -  gmake[3]: *** [/builds/worker/checkouts/gecko/config/recurse.mk:72: accessible/mac/target-objects] Error 2
[task 2023-06-27T23:38:38.953Z] 23:38:38     INFO -  gmake[4]: Entering directory '/builds/worker/workspace/obj-build/dom/battery'

The non-unified build tasks are kicking my butt. Last time I land this, promise.

https://hg.mozilla.org/mozilla-central/rev/3d4299408fc4