Chrobalt build acceleration.

Set up Chrobalt build acceleration with RBE making it the default
accelerator for both developers and the CI system.

Remove fetching of RBE cfg files with CIPD. Instead rely on local cfg
files which use public docker images rather than private ones. Taken
from Chromium's trunk.

b/384982606

.github/actions/build/action.yaml

@@ -14,7 +14,7 @@ runs:
         run: echo "$GITHUB_WORKSPACE/depot_tools" >> $GITHUB_PATH
         shell: bash
       - name: Generate gclient file
-        run: gclient config --name=src https://github.com/${{ github.repository }}
+        run: gclient config --name=src https://github.com/${{ github.repository }} --custom-var=download_remoteexec_cfg=True --custom-var='rbe_instance="projects/cobalt-actions-prod/instances/default_instance"'
         shell: bash
       - name: Set target OS for Android
         if: ${{ contains(matrix.platform, 'android') }}
@@ -25,9 +25,6 @@ runs:
       - name: Gclient sync
         run: gclient sync -v --shallow --no-history -r ${{ github.sha }}
         shell: bash
-      - name: sccache check
-        run: sccache -s
-        shell: bash
       - name: gn gen
         run: |
           cd src
@@ -46,9 +43,6 @@ runs:
           cd src
           ninja -C out/${{ matrix.platform }}_${{ matrix.config }} $(echo "${TARGETS}" | tr -d '"')
         shell: bash
-      - name: Dump sccache stats
-        run: sccache -s
-        shell: bash
       - name: Archive Android APKs
         if: startsWith(matrix.platform, 'android') && matrix.config == 'qa'
         uses: actions/upload-artifact@v4

buildtools/reclient_cfgs/fetch_reclient_cfgs.py

@@ -134,6 +134,10 @@ def main():
             return 1
         if not GenerateReproxyCfg(args.reproxy_cfg_template, args.rbe_instance):
            return 1
+# COBALT Disables CIPD fetch of rewrapper configs in favor of local rewrapper configs.
+        return 0
+    return 1
+# COBALT END
 
     if not args.rewrapper_cfg_project and not args.rbe_instance:
         logging.error(

cobalt/build/gn.py

@@ -85,10 +85,9 @@ def write_build_args(build_args_path, original_lines, dict_settings,
         f'The following args cannot be set in configs: {controlled_args}')
   gen_comment = '# Set by gn.py'
   with open(build_args_path, 'w', encoding='utf-8') as f:
-    if os.getenv('IS_CI', default='0') == '1':
-      f.write(f'cc_wrapper = "{CC_WRAPPER}" {gen_comment}\n')
-    else:
-      f.write(f'use_remoteexec = true {gen_comment}\n')
+    f.write(f'use_remoteexec = true {gen_comment}\n')
+    f.write(
+        f'rbe_cfg_dir = rebase_path("//cobalt/reclient_cfgs") {gen_comment}\n')
     f.write(f'build_type = "{build_type}" {gen_comment}\n')
     for key, value in _BUILD_TYPES[build_type].items():
       f.write(f'{key} = {value} {gen_comment}\n')

cobalt/reclient_cfgs/chromium-browser-clang/rewrapper_linux.cfg

@@ -0,0 +1,8 @@
+platform=container-image=docker://gcr.io/chops-public-images-prod/rbe/siso-chromium/linux@sha256:26de99218a1a8b527d4840490bcbf1690ee0b55c84316300b60776e6b3a03fe1,label:action_default=1
+server_address=unix:///tmp/reproxy.sock
+labels=type=compile,compiler=clang,lang=cpp
+exec_strategy=remote_local_fallback
+dial_timeout=10m
+exec_timeout=2m
+reclient_timeout=2m
+canonicalize_working_dir=true

cobalt/reclient_cfgs/python/rewrapper_linux.cfg

@@ -0,0 +1,8 @@
+platform=container-image=docker://gcr.io/chops-public-images-prod/rbe/siso-chromium/linux@sha256:26de99218a1a8b527d4840490bcbf1690ee0b55c84316300b60776e6b3a03fe1,label:action_default=1
+server_address=unix:///tmp/reproxy.sock
+labels=type=tool
+exec_strategy=remote_local_fallback
+dial_timeout=10m
+canonicalize_working_dir=true
+exec_timeout=2m
+reclient_timeout=2m