We haven't actually used the SwCompositor's native GL mode since the early days of prototyping, and since then, we've veered in the direction of preferring to have the platform native compositor code living in webrender_bindings.

The native GL mode has likely bit-rotted beyond actually functioning and just adds unnecessary complexity to the code, so let's just remove it.

Backed out for wrench failures

backout: https://hg.mozilla.org/integration/autoland/rev/189bd7b21ced559b915493c7feb8e88390452e14

push: https://treeherder.mozilla.org/jobs?repo=autoland&selectedTaskRun=B7qmpgodT2-j0vZl6X0xog.0&searchStr=linux%2Cx64%2Cwebrender%2Copt%2Cwebrender%2Cstandalone%2Cwebrender-linux64-release%2Cwrench&revision=7443389d02050e90195a14c17902885149e8e236

failure log: https://treeherder.mozilla.org/logviewer?job_id=333411576&repo=autoland&lineNumber=34956

[task 2021-03-16T17:25:44.597Z]      Running `rustc --crate-name wrench --edition=2018 wrench/src/main.rs --error-format=json --json=diagnostic-rendered-ansi --crate-type bin --emit=dep-info,link -C opt-level=3 -C panic=abort -C embed-bitcode=no -C debuginfo=2 --cfg 'feature="default"' --cfg 'feature="env_logger"' --cfg 'feature="software"' --cfg 'feature="swgl"' -C metadata=12a71869cc3c591f -C extra-filename=-12a71869cc3c591f --out-dir /builds/worker/checkouts/gecko/gfx/wr/target/release/deps -L dependency=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps --extern base64=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libbase64-a0a803bd46c27642.rlib --extern chrono=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libchrono-84700ac5cccedfeb.rlib --extern clap=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libclap-9ab22928d7a13aee.rlib --extern crossbeam=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libcrossbeam-21558df9658d5853.rlib --extern env_logger=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libenv_logger-e992d802ff54135f.rlib --extern font_loader=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libfont_loader-a999350718ec20c1.rlib --extern gleam=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libgleam-89c0e894ead7c102.rlib --extern glutin=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libglutin-94b374b77b1c5ce9.rlib --extern image=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libimage-8787b6c6272940b0.rlib --extern log=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/liblog-b803d17e6ccc6d56.rlib --extern semver=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libsemver-08176c7423e21d17.rlib --extern serde=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libserde-8b4c8272a3f4e6f5.rlib --extern serde_json=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libserde_json-2499f333ada48af6.rlib --extern swgl=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libswgl-7cfcf3a1589ba199.rlib --extern time=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libtime-c015eea573fa83c4.rlib --extern tracy_rs=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libtracy_rs-cb344e83ae1b317e.rlib --extern webrender=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libwebrender-2169f2e9079c657b.rlib --extern winit=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libwinit-d717b298b1751bf5.rlib --extern yaml_rust=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libyaml_rust-2430bb471f7e9023.rlib --deny warnings -L native=/usr/lib/x86_64-linux-gnu -L native=/usr/lib/x86_64-linux-gnu -L native=/usr/lib/x86_64-linux-gnu -L native=/builds/worker/checkouts/gecko/gfx/wr/target/release/build/libloading-26ed1a94576b1010/out -L native=/builds/worker/checkouts/gecko/gfx/wr/target/release/build/swgl-d3ed6b78237da2b9/out`
[task 2021-03-16T17:25:45.055Z] error[E0599]: no method named `get_color_buffer` found for reference `&swgl::Context` in the current scope
[task 2021-03-16T17:25:45.055Z]    --> wrench/src/main.rs:161:45
[task 2021-03-16T17:25:45.055Z]     |
[task 2021-03-16T17:25:45.055Z] 161 |         let (data_ptr, w, h, stride) = swgl.get_color_buffer(0, true);
[task 2021-03-16T17:25:45.055Z]     |                                             ^^^^^^^^^^^^^^^^ method not found in `&swgl::Context`
[task 2021-03-16T17:25:45.055Z] 
[task 2021-03-16T17:25:45.430Z] error: aborting due to previous error
[task 2021-03-16T17:25:45.430Z] 
[task 2021-03-16T17:25:45.430Z] For more information about this error, try `rustc --explain E0599`.
[task 2021-03-16T17:25:45.460Z] error: could not compile `wrench`
[task 2021-03-16T17:25:45.460Z] 
[task 2021-03-16T17:25:45.460Z] Caused by:
[task 2021-03-16T17:25:45.460Z]   process didn't exit successfully: `rustc --crate-name wrench --edition=2018 wrench/src/main.rs --error-format=json --json=diagnostic-rendered-ansi --crate-type bin --emit=dep-info,link -C opt-level=3 -C panic=abort -C embed-bitcode=no -C debuginfo=2 --cfg 'feature="default"' --cfg 'feature="env_logger"' --cfg 'feature="software"' --cfg 'feature="swgl"' -C metadata=12a71869cc3c591f -C extra-filename=-12a71869cc3c591f --out-dir /builds/worker/checkouts/gecko/gfx/wr/target/release/deps -L dependency=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps --extern base64=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libbase64-a0a803bd46c27642.rlib --extern chrono=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libchrono-84700ac5cccedfeb.rlib --extern clap=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libclap-9ab22928d7a13aee.rlib --extern crossbeam=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libcrossbeam-21558df9658d5853.rlib --extern env_logger=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libenv_logger-e992d802ff54135f.rlib --extern font_loader=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libfont_loader-a999350718ec20c1.rlib --extern gleam=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libgleam-89c0e894ead7c102.rlib --extern glutin=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libglutin-94b374b77b1c5ce9.rlib --extern image=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libimage-8787b6c6272940b0.rlib --extern log=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/liblog-b803d17e6ccc6d56.rlib --extern semver=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libsemver-08176c7423e21d17.rlib --extern serde=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libserde-8b4c8272a3f4e6f5.rlib --extern serde_json=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libserde_json-2499f333ada48af6.rlib --extern swgl=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libswgl-7cfcf3a1589ba199.rlib --extern time=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libtime-c015eea573fa83c4.rlib --extern tracy_rs=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libtracy_rs-cb344e83ae1b317e.rlib --extern webrender=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libwebrender-2169f2e9079c657b.rlib --extern winit=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libwinit-d717b298b1751bf5.rlib --extern yaml_rust=/builds/worker/checkouts/gecko/gfx/wr/target/release/deps/libyaml_rust-2430bb471f7e9023.rlib --deny warnings -L native=/usr/lib/x86_64-linux-gnu -L native=/usr/lib/x86_64-linux-gnu -L native=/usr/lib/x86_64-linux-gnu -L native=/builds/worker/checkouts/gecko/gfx/wr/target/release/build/libloading-26ed1a94576b1010/out -L native=/builds/worker/checkouts/gecko/gfx/wr/target/release/build/swgl-d3ed6b78237da2b9/out` (exit code: 1)
[taskcluster 2021-03-16 17:25:45.789Z] === Task Finished ===
[taskcluster 2021-03-16 17:25:45.789Z] Unsuccessful task run with exit code: 101 completed in 449.401 seconds

https://hg.mozilla.org/mozilla-central/rev/c2ad88081295