Experimental/m138 lw exclude chrome (#7291)

This PR enables the use of exclude_chrome_build=true for lightweight
Linux builds.
With this change, it is possible to build essential Chromium components
without including the full Chrome browser dependencies.

It also ensures that chromedriver remains available for testing and
automation, even in lightweight builds.

This is applied to Linux only as exclude_chrome_build currently supports
Linux, and Android lightweight builds don't require GN-level exclusion.

Author: yunsik-jung

BUILD.gn

@@ -9,6 +9,7 @@
 # file to your new one or GN won't know about it.
 
 import("//build/config/cast.gni")
+import("//build/config/chrome_exclude.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/cronet/config.gni")
 import("//build/config/dcheck_always_on.gni")
@@ -149,7 +150,7 @@ group("gn_all") {
     }
 
     if (!is_ios && !is_android && !is_castos) {
-      if (!is_fuchsia) {
+      if (!exclude_chrome_build) {
         deps += [
           "//chrome",
           "//chrome/browser/ui/actions:dump_actions",
@@ -171,15 +172,15 @@ group("gn_all") {
       ]
     }
 
-    if (!is_castos && !is_fuchsia) {
+    if (!exclude_chrome_build) {
       deps += [ "//chrome/installer" ]
     }
 
-    if (!is_fuchsia && enable_updater) {
+    if (!exclude_chrome_build && enable_updater) {
       deps += [ "//chrome/updater" ]
     }
 
-    if (enable_enterprise_companion) {
+    if (enable_enterprise_companion && !exclude_chrome_build) {
       deps += [ "//chrome/enterprise_companion" ]
     }
 
@@ -191,7 +192,7 @@ group("gn_all") {
     }
 
     if (!is_ios && !is_castos) {
-      if (!is_fuchsia) {
+      if (!exclude_chrome_build) {
         deps += [ "//chrome/test:unit_tests" ]
       }
       deps += [ "//ui/accessibility:accessibility_unittests" ]
@@ -261,7 +262,7 @@ group("gn_all") {
         "//third_party/catapult/telemetry:bitmaptools($host_toolchain)",
       ]
       if (!is_android) {
-        if (!is_castos && !is_fuchsia) {
+        if (!exclude_chrome_build) {
           deps += [ "//chrome/test:telemetry_perf_unittests" ]
         }
       } else {
@@ -331,7 +332,7 @@ group("gn_all") {
       ]
     }
 
-    if (enterprise_watermark) {
+    if (enterprise_watermark && !exclude_chrome_build) {
       deps += [ "//chrome/browser/enterprise/watermark:watermark_app" ]
     }
 
@@ -497,7 +498,7 @@ group("gn_all") {
         deps += [ "//testing:empty_main" ]
       }
 
-      if (!is_castos) {
+      if (!exclude_chrome_build) {
         deps += [ "//chrome:xdg_mime" ]
       }
 
@@ -555,7 +556,7 @@ group("gn_all") {
         ]
       }
 
-      if (!is_android && !is_castos && !is_ios && !is_fuchsia) {
+      if (!is_android && !is_ios && !exclude_chrome_build) {
         deps += [
           "//chrome/test:load_library_perf_tests",
           "//chrome/test:sync_performance_tests",
@@ -626,7 +627,7 @@ group("gn_all") {
         "//ui/snapshot:snapshot_unittests",
       ]
 
-      if (!is_castos) {
+      if (!exclude_chrome_build) {
         deps += [ "//chrome/test:chrome_app_unittests" ]
       }
 
@@ -757,8 +758,6 @@ group("gn_all") {
       # TODO(https://crbug.com/1329673): Figure out if any of these should be in
       # gn_all and figure out how cross-platform they are.
       deps += [
-        "//chrome/installer/util:strings",
-        "//chrome/tools/convert_dict",
         "//components/constrained_window:unit_tests",
         "//components/metrics:serialization",
         "//components/sessions:unit_tests",
@@ -778,8 +777,15 @@ group("gn_all") {
         "//ui/shell_dialogs:shell_dialogs_unittests",
       ]
 
+      if (!exclude_chrome_build) {
+        deps += [
+          "//chrome/installer/util:strings",
+          "//chrome/tools/convert_dict",
+        ]
+      }
+
       if (target_cpu == "x86" || target_cpu == "x64") {
-        if (!is_android) {
+        if (!is_android && !exclude_chrome_build) {
           deps += [ "//chrome/test:load_library_perf_tests" ]
         }
         deps += [ "//third_party/libjpeg_turbo:simd_asm" ]
@@ -817,7 +823,7 @@ group("gn_all") {
       ]
     }
 
-    if (enable_vr) {
+    if (enable_vr && !exclude_chrome_build) {
       deps += [
         "//chrome/browser/vr:vr_common_perftests",
         "//chrome/browser/vr:vr_common_unittests",
@@ -1127,7 +1133,7 @@ if (use_blink && !is_cronet_build) {
       "//third_party/blink/public:all_blink",
     ]
 
-    if (!is_chromeos && !is_ios && !is_fuchsia && !is_android && !is_castos) {
+    if (!is_chromeos && !is_ios && !is_android && !exclude_chrome_build) {
       deps += [
         ":chrome_wpt_tests",
         ":headless_shell_wpt",
@@ -1181,7 +1187,7 @@ if (use_blink && !is_cronet_build) {
     ]
   }
 
-  if (!is_chromeos && !is_ios && !is_fuchsia && !is_android && !is_castos) {
+  if (!is_chromeos && !is_ios && !is_android && !exclude_chrome_build) {
     # https://chromium.googlesource.com/chromium/src/+/HEAD/docs/testing/run_web_platform_tests.md
     script_test("chrome_wpt_tests") {
       script = "//third_party/blink/tools/run_wpt_tests.py"
@@ -1731,14 +1737,14 @@ group("chromium_builder_perf") {
       "//tools/perf/chrome_telemetry_build:telemetry_chrome_test",
     ]
 
-    if (!is_fuchsia) {
+    if (!exclude_chrome_build) {
       data_deps += [
         "//chrome/test:load_library_perf_tests",
         "//chrome/test:performance_test_suite",
       ]
     }
 
-    if (!is_chromeos && !is_fuchsia) {
+    if (!is_chromeos && !exclude_chrome_build) {
       data_deps += [ "//chrome/test:performance_browser_tests" ]
     }
 
@@ -1776,7 +1782,7 @@ if (!is_ios && !is_android && !is_castos && !is_cronet_build) {
       "//third_party/blink/public/mojom:mojom_modules_js",
       "//v8:d8",
     ]
-    if (!is_fuchsia) {
+    if (!exclude_chrome_build) {
       deps += [ "//chrome:chrome" ]
     }
     if (!is_win) {

build/config/chrome_exclude.gni

@@ -0,0 +1,33 @@
+# Copyright 2025 The Chromium Authors
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("//build/config/cast.gni")
+import("//build/config/lightweight.gni")
+
+declare_args() {
+  # Controls whether to exclude //chrome directory from the build graph.
+  # This prevents unnecessary GN failures caused by //chrome dependencies when
+  # building only specific Chromium components without the Chrome browser.
+  #
+  # When true:
+  # - //chrome targets are excluded from the build
+  # - Prevents GN failures from unwanted //chrome dependencies
+  #
+  # Supported platforms:
+  # - Fuchsia, CastOS: Always true
+  # - Linux: Optional
+  #
+  # TODO: Consider adding is_cast_android support.
+  exclude_chrome_build =
+      is_fuchsia || is_castos || (enable_lightweight && !is_android)
+}
+
+if (exclude_chrome_build && !(is_fuchsia || is_castos || is_linux)) {
+  print("WARNING: exclude_chrome_build=true is only supported on Fuchsia, " +
+        "CastOS, and Linux platforms.")
+}
+
+# For Fuchsia and CastOS, exclude_chrome_build must be true.
+assert(!(is_fuchsia || is_castos) || exclude_chrome_build,
+       "exclude_chrome_build must be true for Fuchsia and CastOS.")