LaCrOS: Replace defined(OS_CHROMEOS) with BUILDFLAG(IS_CHROMEOS_ASH)

The change is mostly mechanical replacing defined(OS_CHROMEOS) with
BUILDFLAG(IS_CHROMEOS_ASH) and GN variable is_chromeos with is_ash
with some special cases (For those cases please refer to
http://go/lacros-macros).

The patch is made in preparation to switching lacros build from
target_os=linux to target_os=chromeos. This will prevent lacros from
changing behaviour after the switch.

Bug: 1052397
Change-Id: I4496e16926e171cbaa4bc68b92d39490a07c1cf9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2531811
Commit-Queue: Yuta Hijikata <ythjkt@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@google.com>
Cr-Commit-Position: refs/heads/master@{#828635}

tools/grit/grit_defines.gni

@@ -48,21 +48,21 @@ if (is_chrome_branded) {
   ]
 }
 
-if (is_chromeos) {
+if (is_chromeos_ash) {
   grit_defines += [
     "-D",
     "chromeos",
   ]
 }
 
-if (chromeos_is_browser_only) {
+if (is_chromeos_lacros) {
   grit_defines += [
     "-D",
     "lacros",
   ]
 }
 
-if (is_linux) {
+if (is_linux || is_chromeos_lacros) {
   grit_defines += [
     "-D",
     "desktop_linux",

tools/ipc_fuzzer/fuzzer/BUILD.gn

@@ -2,6 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/config/chromeos/ui_mode.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 
 executable("ipc_fuzzer") {
@@ -24,7 +25,7 @@ executable("ipc_fuzzer") {
     "//tools/ipc_fuzzer/message_lib:ipc_message_lib",
   ]
   public_deps = [ "//ipc" ]
-  if (is_asan && is_chromeos) {
+  if (is_asan && is_chromeos_ash) {
     # Compiling fuzzer.cc with ASan takes too long, see
     # http://crbug.com/360158.
     configs -= [ "//build/config/sanitizers:default_sanitizer_flags" ]

tools/perf/chrome_telemetry_build/BUILD.gn

@@ -2,12 +2,13 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/config/chromeos/ui_mode.gni")
 import("//build/config/compiler/compiler.gni")
 if (is_android) {
   # Pull in enable_chrome_android_internal and public_android_sdk
   import("//build/config/android/config.gni")
 }
-if (is_chromeos) {
+if (is_chromeos_ash) {
   import("//build/config/chromeos/rules.gni")
 }
 
@@ -49,7 +50,7 @@ group("telemetry_chrome_test") {
     # CrOS currently has issues with the locally compiled version of
     # crashpad_database_util, so only include it on traditional Linux
     # platforms.
-    if (is_linux) {
+    if (is_linux || is_chromeos_lacros) {
       data_deps +=
           [ "//third_party/crashpad/crashpad/tools:crashpad_database_util" ]
     }
@@ -64,7 +65,7 @@ group("telemetry_chrome_test") {
     ]
   }
 
-  if (is_chromeos && is_chromeos_device) {
+  if (is_chromeos_ash && is_chromeos_device) {
     data_deps += [
       "//:chromiumos_preflight",
       "//chromeos:cros_chrome_deploy",

tools/v8_context_snapshot/v8_context_snapshot.gni

@@ -8,6 +8,7 @@
 # to speedup creating a V8 context and setting up around it.
 
 import("//build/config/chromecast_build.gni")
+import("//build/config/chromeos/ui_mode.gni")
 import("//build/config/v8_target_cpu.gni")
 import("//v8/gni/v8.gni")
 
@@ -15,7 +16,7 @@ declare_args() {
   # TODO(crbug.com/764576): Enable the feature on more environments.
   # Disable in mac and win cross builds since building Blink twice is slow.
   use_v8_context_snapshot =
-      !is_chromeos && !is_android && !is_chromecast && !is_fuchsia &&
+      !is_chromeos_ash && !is_android && !is_chromecast && !is_fuchsia &&
       !(host_os == "mac" && current_cpu == "x86") &&
       (v8_target_cpu == target_cpu || is_msan) &&
       !(is_win && host_os != "win") && !(is_mac && host_os != "mac")