Lacros: Define BUILDFLAG(IS_CHROMSOS_ASH|LACROS).

Lacros team has decided to rename gn variable is_ash|lacros and macro
IS_ASH|LACROS as is_chromeos_ash|lacros and IS_CHROMEOS_ASH|LACROS
respectively. This is to make it clearer that these variables are Chrome
OS related variables.

Bug: 1052397
Change-Id: I7e74ef50af0695809340f9d3645de6487494334e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2502061
Commit-Queue: Yuta Hijikata <ythjkt@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#821730}

build/BUILD.gn

@@ -39,7 +39,11 @@ buildflag_header("chromeos_buildflags") {
 
   flags = [
     "IS_CHROMEOS_DEVICE=$is_chromeos_device",
-    "IS_LACROS=$chromeos_is_browser_only",
-    "IS_ASH=$is_ash",
+
+    # TODO(crbug.com/1052397): Remove IS_LACROS|ASH once all of them are replaced by IS_CHROMEOS_*.
+    "IS_LACROS=$is_chromeos_lacros",
+    "IS_ASH=$is_chromeos_ash",
+    "IS_CHROMEOS_LACROS=$is_chromeos_lacros",
+    "IS_CHROMEOS_ASH=$is_chromeos_ash",
   ]
 }

build/config/chromeos/ui_mode.gni

@@ -23,7 +23,14 @@ declare_args() {
   also_build_ash_chrome = false
 }
 
-is_ash = is_chromeos && !chromeos_is_browser_only
+# is_chromeos_ash|lacros is used to specify that it is specific to either
+# ash or lacros chrome for chromeos. For platform specific logic that
+# applies to both, use is_chromeos instead.
+is_chromeos_ash = is_chromeos && !chromeos_is_browser_only
+is_chromeos_lacros = chromeos_is_browser_only
 
-# Temporarily define is_lacros as an alias.
-is_lacros = chromeos_is_browser_only
+# TODO(crbug.com/1052397):
+# Remove is_ash|lacros once all are replaced by is_chromeos_*.
+# is_ash|lacros is deprecated. Use is_chromeos_ash|lacros instead.
+is_ash = is_chromeos_ash
+is_lacros = is_chromeos_lacros