Now that they're both based on CUPS there's no need to have three of these. They're basically copy-pasta.

nsPrinterListBase is where the CC setup and promises and such will be, I
think.

Depends on D86336

Now that we share the list code between GTK and Mac, there's no reason
for this. This also avoids work when getting the default printer name.

Backed out changeset a71e53a3e455 (bug 1657874) for CUPSPrinterList.h related bustage

Push with failures: https://treeherder.mozilla.org/#/jobs?repo=autoland&group_state=expanded&searchStr=build&fromchange=5860b7b7c7a435fc09b05af7f19242662cdc7a1c&tochange=b63b993e5e56cbe1ac27d39a5d868639d730a827&selectedTaskRun=WeGHaZ7aRCeXCTHnGXhlWA.0

Backout link: https://hg.mozilla.org/integration/autoland/rev/b63b993e5e56cbe1ac27d39a5d868639d730a827

Failure log: https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=312383182&repo=autoland&lineNumber=44044

[task 2020-08-07T12:31:17.386Z] 12:31:17     INFO -  make[4]: Entering directory '/builds/worker/workspace/obj-build/widget/gtk'
[task 2020-08-07T12:31:17.391Z] 12:31:17     INFO -  /builds/worker/fetches/sccache/sccache /builds/worker/fetches/clang/bin/clang++ -std=gnu++17 -o Unified_cpp_widget_gtk1.o -c  -I/builds/worker/workspace/obj-build/dist/stl_wrappers -I/builds/worker/workspace/obj-build/dist/system_wrappers -include /builds/worker/checkouts/gecko/config/gcc_hidden.h -U_FORTIFY_SOURCE -fno-common -DNDEBUG=1 -DTRIMMED=1 -DOS_POSIX=1 -DOS_LINUX=1 -DCAIRO_GFX '-DMOZ_APP_NAME="firefox"' -DMOZ_HAS_MOZGLUE -DMOZILLA_INTERNAL_API -DIMPL_LIBXUL -DSTATIC_EXPORTABLE_JS_API -I/builds/worker/checkouts/gecko/widget/gtk -I/builds/worker/workspace/obj-build/widget/gtk -I/builds/worker/workspace/obj-build/ipc/ipdl/_ipdlheaders -I/builds/worker/checkouts/gecko/ipc/chromium/src -I/builds/worker/checkouts/gecko/ipc/glue -I/builds/worker/checkouts/gecko/layout/base -I/builds/worker/checkouts/gecko/layout/forms -I/builds/worker/checkouts/gecko/layout/generic -I/builds/worker/checkouts/gecko/layout/xul -I/builds/worker/checkouts/gecko/other-licenses/atk-1.0 -I/builds/worker/checkouts/gecko/third_party/cups/include -I/builds/worker/checkouts/gecko/widget -I/builds/worker/checkouts/gecko/widget/headless -I/builds/worker/checkouts/gecko/widget/x11 -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 -fPIC -DMOZILLA_CLIENT -include /builds/worker/workspace/obj-build/mozilla-config.h -Qunused-arguments -Qunused-arguments -Wall -Wbitfield-enum-conversion -Wempty-body -Wignored-qualifiers -Woverloaded-virtual -Wpointer-arith -Wshadow-field-in-constructor-modified -Wsign-compare -Wtype-limits -Wunreachable-code -Wunreachable-code-return -Wwrite-strings -Wno-invalid-offsetof -Wclass-varargs -Wempty-init-stmt -Wfloat-overflow-conversion -Wfloat-zero-conversion -Wloop-analysis -Wc++2a-compat -Wcomma -Wimplicit-fallthrough -Wunused-function -Wunused-variable -Werror=non-literal-null-conversion -Wstring-conversion -Wtautological-overlap-compare -Wtautological-unsigned-enum-zero-compare -Wtautological-unsigned-zero-compare -Wno-error=tautological-type-limit-compare -Wno-inline-new-delete -Wno-error=deprecated-declarations -Wno-error=array-bounds -Wno-error=backend-plugin -Wno-error=return-std-move -Wno-error=atomic-alignment -Wformat -Wformat-security -Wno-gnu-zero-variadic-macro-arguments -Werror=implicit-function-declaration -Wno-unknown-warning-option -D_GLIBCXX_USE_CXX11_ABI=0 -fno-sized-deallocation -fno-aligned-new -fsanitize=bool,bounds,enum,integer-divide-by-zero,object-size,pointer-overflow,return,vla-bound -fno-sanitize-recover=bool,bounds,enum,integer-divide-by-zero,object-size,pointer-overflow,return,vla-bound -fsanitize-blacklist=/builds/worker/workspace/obj-build/ubsan_blacklist.txt -fsanitize=address -fcrash-diagnostics-dir=/builds/worker/artifacts -fno-exceptions -fno-strict-aliasing -fno-rtti -ffunction-sections -fdata-sections -fno-exceptions -fno-math-errno -pthread -pipe -g -Xclang -load -Xclang /builds/worker/workspace/obj-build/build/clang-plugin/libclang-plugin.so -Xclang -add-plugin -Xclang moz-check -O2 -gline-tables-only -fno-omit-frame-pointer -funwind-tables -Werror -I/builds/worker/checkouts/gecko/widget/gtk/compat-gtk3 -pthread -I/usr/include/gtk-3.0/unix-print -I/usr/include/gtk-3.0 -I/usr/include/at-spi2-atk/2.0 -I/usr/include/at-spi-2.0 -I/usr/include/dbus-1.0 -I/usr/lib/x86_64-linux-gnu/dbus-1.0/include -I/usr/include/gtk-3.0 -I/usr/include/cairo -I/usr/include/pango-1.0 -I/usr/include/harfbuzz -I/usr/include/pango-1.0 -I/usr/include/atk-1.0 -I/usr/include/cairo -I/usr/include/pixman-1 -I/usr/include/freetype2 -I/usr/include/libpng12 -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/libpng12 -I/usr/include/gio-unix-2.0/ -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include -pthread -I/usr/include/gtk-3.0 -I/usr/include/at-spi2-atk/2.0 -I/usr/include/at-spi-2.0 -I/usr/include/dbus-1.0 -I/usr/lib/x86_64-linux-gnu/dbus-1.0/include -I/usr/include/gtk-3.0 -I/usr/include/gio-unix-2.0/ -I/usr/include/cairo -I/usr/include/pango-1.0 -I/usr/include/harfbuzz -I/usr/include/pango-1.0 -I/usr/include/atk-1.0 -I/usr/include/cairo -I/usr/include/pixman-1 -I/usr/include/freetype2 -I/usr/include/libpng12 -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/libpng12 -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include -I/usr/include/libdrm -I/usr/include/dbus-1.0 -I/usr/lib/x86_64-linux-gnu/dbus-1.0/include -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include -Wno-error=shadow -fexperimental-new-pass-manager  -MD -MP -MF .deps/Unified_cpp_widget_gtk1.o.pp   Unified_cpp_widget_gtk1.cpp
[task 2020-08-07T12:31:17.392Z] 12:31:17     INFO -  In file included from Unified_cpp_widget_gtk1.cpp:137:
[task 2020-08-07T12:31:17.392Z] 12:31:17     INFO -  /builds/worker/checkouts/gecko/widget/gtk/nsDeviceContextSpecG.cpp:22:10: fatal error: 'CUPSPrinterList.h' file not found
[task 2020-08-07T12:31:17.393Z] 12:31:17     INFO -  #include "CUPSPrinterList.h"
[task 2020-08-07T12:31:17.397Z] 12:31:17     INFO -           ^~~~~~~~~~~~~~~~~~~
[task 2020-08-07T12:31:17.397Z] 12:31:17     INFO -  1 error generated.
[task 2020-08-07T12:31:17.397Z] 12:31:17     INFO -  /builds/worker/checkouts/gecko/config/rules.mk:718: recipe for target 'Unified_cpp_widget_gtk1.o' failed
[task 2020-08-07T12:31:17.397Z] 12:31:17    ERROR -  make[4]: *** [Unified_cpp_widget_gtk1.o] Error 1
[task 2020-08-07T12:31:17.397Z] 12:31:17     INFO -  make[4]: Leaving directory '/builds/worker/workspace/obj-build/widget/gtk'

https://hg.mozilla.org/mozilla-central/rev/b829e396f4de
https://hg.mozilla.org/mozilla-central/rev/5860b7b7c7a4

https://hg.mozilla.org/mozilla-central/rev/5973309ec843

What's the status here? Can we close this?