Remove IS_CHROMEOS_ASH from //components/*

This cleans up the following subdirectories: sessions,
soda, storage_monitor, supervised_user, sync_preferences,
system_media_controls, translate, trusted_vault,
unified_consent, update_client, user_manager,
vector_icons, version_ui, web_resource

1) Removed IS_CHROMEOS_LACROS usages and code it guarded
2) Renamed IS_CHROMEOS_ASH to IS_CHROMEOS
3) Removed chromeos_buildflags.h includes
4) Cleaned up *.gn files from IS_CHROMEOS_*.

Bug: 375523816, 373972275, 373971535
Change-Id: I973920d2078526bede68a84dbea53029d202c22d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6097194
Reviewed-by: Georg Neis <[email protected]>
Reviewed-by: Nico Weber <[email protected]>
Commit-Queue: Maksim Sisov <[email protected]>
Reviewed-by: Hidehiko Abe <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1397771}
diff --git a/components/storage_monitor/mtab_watcher_linux.h b/components/storage_monitor/mtab_watcher_linux.h
index 69687f6..0f1fabe 100644
--- a/components/storage_monitor/mtab_watcher_linux.h
+++ b/components/storage_monitor/mtab_watcher_linux.h
@@ -5,12 +5,6 @@
 #ifndef COMPONENTS_STORAGE_MONITOR_MTAB_WATCHER_LINUX_H_
 #define COMPONENTS_STORAGE_MONITOR_MTAB_WATCHER_LINUX_H_
 
-#include "build/chromeos_buildflags.h"
-
-#if BUILDFLAG(IS_CHROMEOS_ASH)
-#error "ChromeOS does not use MtabWatcherLinux."
-#endif
-
 #include <map>
 
 #include "base/files/file_path.h"
@@ -19,6 +13,10 @@
 #include "base/sequence_checker.h"
 #include "build/build_config.h"
 
+#if BUILDFLAG(IS_CHROMEOS)
+#error "ChromeOS does not use MtabWatcherLinux."
+#endif
+
 namespace storage_monitor {
 
 // MtabWatcherLinux listens for mount point changes from a mtab file and