arch/chromium-fourier: scaffold PKGBUILD + placeholder patch

Initial chromium-fourier shape on the chromium-builder@boltzmann LXD
container we provisioned today. Approach is the 7Ji-style "tarball +
system tools" pattern (no gclient/CIPD, the linux-arm64 dependency
binaries don't exist anyway) but stripped of the MPP/X11/panfork
specifics — chromium-fourier targets mainline kernel + Wayland +
panfrost/panthor + V4L2 stateless on /dev/video0, not the vendor
stack 7Ji's chromium-mpp targets.

PKGBUILD highlights:
- pkgver=147.0.7727.116 (current Chrome stable as of 2026-04-25)
- gn args: use_v4l2_codec=true, use_v4lplugin=true, use_linux_v4l2_only=true,
  use_vaapi=true. The first three are the magic that unlocks V4L2VDA on
  Linux non-ChromeOS without source patches; if they're sufficient on
  their own, the chromeos-pipeline-bypass patch stays a no-op.
- ffmpeg_branding="Chrome" + proprietary_codecs=true for H.264.
- enable_widevine=false, enable_nacl=false to keep the tree small.
- Currently development-shaped: prepare()/build() operate on a
  pre-extracted /build/chromium/src rather than makepkg-fetched
  source. Will switch to canonical source=(...tarball.xz) shape once
  the patches stabilise.

patches/chromeos-pipeline-bypass.patch is a placeholder; the actual
patch (if any) gets developed once we see what 7Ji's gn args do or
don't unlock for us.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

arch/chromium-fourier/PKGBUILD

@@ -0,0 +1,166 @@
+# Maintainer: Markus Fritsche <mfritsche@reauktion.de>
+#
+# Chromium with V4L2 HW video decode unlocked on Linux for Rockchip
+# (RK3566 hantro / RK3588 VDPU381) on **mainline** kernel + Wayland +
+# panfrost / panthor — no vendor MPP, no Mali blob, no panfork, no
+# 5.10 BSP kernel. Fills the niche that 7Ji's chromium-mpp explicitly
+# does not (it forces BSP + X11 + vendor stack); see
+# /home/mfritsche/src/marfrit-packages/arch/chromium-fourier/STUDY.md
+# for the full rationale.
+#
+# Build host: chromium-builder LXD container on boltzmann (8 cores,
+# 28 GB RAM cap, 824 GB NVMe). 6-10 h initial build.
+
+pkgname=chromium-fourier
+pkgver=147.0.7727.116
+pkgrel=1
+epoch=1
+pkgdesc='Chromium with V4L2VDA HW video decode unlocked for mainline Linux Wayland on Rockchip'
+arch=('aarch64')
+url='https://www.chromium.org/Home'
+license=('BSD-3-Clause')
+depends=(
+  alsa-lib
+  at-spi2-core
+  cairo
+  cups
+  dbus
+  fontconfig
+  freetype2
+  gtk3
+  hicolor-icon-theme
+  libdrm
+  libpulse
+  libva
+  libxcb
+  libxkbcommon
+  mesa
+  nspr
+  nss
+  pango
+  pciutils
+  pipewire
+  ttf-liberation
+  v4l-utils
+  wayland
+)
+makedepends=(
+  clang
+  elfutils
+  gn
+  gperf
+  java-runtime-headless
+  libxslt
+  lld
+  ninja
+  nodejs
+  npm
+  python
+  qt5-base
+  qt6-base
+  re2
+  rust
+  rust-bindgen
+)
+optdepends=(
+  'qt6-base: for Qt6 toolkit integration'
+)
+provides=(chromium)
+conflicts=(chromium)
+options=('!lto' '!strip')
+# NB: the chromium tarball is fetched lazily by build.sh on the build
+# host (5.7 GB compressed, doesn't belong in this git repo). The
+# PKGBUILD assumes /build/chromium/src is already populated.
+source=(
+  'patches/chromeos-pipeline-bypass.patch'
+)
+sha256sums=(
+  'SKIP'
+)
+
+# NB: this PKGBUILD is currently development-shaped — it operates on a
+# pre-extracted chromium tree at /build/chromium/src rather than letting
+# makepkg fetch + unpack the 5.7 GB tarball into ${srcdir}. Once the
+# patches stabilise we'll switch to the canonical pattern with
+# source=(${url}/chromium-${pkgver}.tar.xz ...) so the standard makepkg
+# flow + CI fermi-style pipeline work end-to-end.
+
+prepare() {
+  cd /build/chromium/src
+
+  # Fourier-local: bypass the chromeos pipeline so VaapiVideoDecoder /
+  # V4L2VDA is reachable on Linux non-ChromeOS. The 7Ji-style gn args
+  # (use_v4l2_codec / use_v4lplugin / use_linux_v4l2_only) may be
+  # sufficient on their own; this patch is the fallback if they aren't.
+  patch -Np1 -i "${srcdir}/patches/chromeos-pipeline-bypass.patch" || true
+
+  # Use system node, system java
+  rm -f third_party/node/linux/node-linux-arm64/bin/node
+  mkdir -p third_party/node/linux/node-linux-arm64/bin
+  ln -sf /usr/bin/node third_party/node/linux/node-linux-arm64/bin/
+  ln -sf /usr/bin/java third_party/jdk/current/bin/ 2>/dev/null || true
+}
+
+build() {
+  cd /build/chromium/src
+
+  local _flags=(
+    'is_official_build=true'
+    'is_debug=false'
+    'symbol_level=0'
+    'is_cfi=false'
+    'treat_warnings_as_errors=false'
+    'enable_nacl=false'
+    'enable_widevine=false'
+
+    # System toolchain (clang/lld from pacman)
+    'custom_toolchain="//build/toolchain/linux/unbundle:default"'
+    'host_toolchain="//build/toolchain/linux/unbundle:default"'
+    'use_sysroot=false'
+    'use_custom_libcxx=true'
+
+    # The whole point of chromium-fourier — V4L2 HW decode on Linux
+    'use_v4l2_codec=true'
+    'use_v4lplugin=true'
+    'use_linux_v4l2_only=true'
+    'use_vaapi=true'
+
+    # Codec branding for proprietary codec support (H.264 etc.)
+    'ffmpeg_branding="Chrome"'
+    'proprietary_codecs=true'
+
+    'rtc_use_pipewire=true'
+    'link_pulseaudio=true'
+    'use_qt6=true'
+    'moc_qt6_path="/usr/lib/qt6"'
+  )
+
+  gn gen out/Default --args="${_flags[*]}"
+  autoninja -C out/Default chrome chromedriver chrome_sandbox
+}
+
+package() {
+  cd /build/chromium/src
+
+  install -Dm755 out/Default/chrome "${pkgdir}/usr/lib/chromium/chromium"
+  install -Dm4755 out/Default/chrome_sandbox "${pkgdir}/usr/lib/chromium/chrome-sandbox"
+  install -Dm755 out/Default/chromedriver "${pkgdir}/usr/bin/chromedriver"
+
+  # Resources / locales / pak files
+  for f in chrome_100_percent.pak chrome_200_percent.pak resources.pak \
+           v8_context_snapshot.bin icudtl.dat headless_lib_data.pak \
+           headless_lib_strings.pak; do
+    [ -f "out/Default/$f" ] && install -Dm644 "out/Default/$f" \
+      "${pkgdir}/usr/lib/chromium/$f"
+  done
+
+  # Locales
+  if [ -d out/Default/locales ]; then
+    install -dm755 "${pkgdir}/usr/lib/chromium/locales"
+    cp -r out/Default/locales/* "${pkgdir}/usr/lib/chromium/locales/"
+  fi
+
+  # Top-level launcher
+  install -dm755 "${pkgdir}/usr/bin"
+  ln -s /usr/lib/chromium/chromium "${pkgdir}/usr/bin/chromium"
+}

arch/chromium-fourier/patches/chromeos-pipeline-bypass.patch

@@ -0,0 +1,22 @@
+From: Markus Fritsche <mfritsche@reauktion.de>
+Subject: media/gpu: skip chromeos VideoDecoderPipeline on non-ChromeOS Linux
+
+Placeholder. The patch will be developed against the actual chromium
+147.0.7727.116 source tree on chromium-builder@boltzmann once the
+tarball is extracted and we can read the exact code paths in:
+
+  - media/gpu/chromeos/video_decoder_pipeline.cc (PickDecoderOutputFormat,
+    Initialize, ImageProcessor setup)
+  - media/gpu/vaapi/vaapi_video_decoder.cc (ApplyResolutionChangeWithScreenSizes,
+    line ~1219 where "failed Initialize()ing the frame pool" fires)
+
+The 7Ji-style gn args (`use_v4l2_codec=true use_v4lplugin=true
+use_linux_v4l2_only=true`) MAY be sufficient by themselves to route
+decode through the legacy V4L2VDA path entirely, bypassing the
+chromeos pipeline without source patches. First build will tell us;
+this file is the placeholder for the patch we'll need if it isn't.
+
+# Empty no-op patch. patch -p1 < this won't change anything.
+diff --git a/PLACEHOLDER b/PLACEHOLDER
+new file mode 100644
+index 0000000..e69de29