Replace CHROMEOS macro with OS_CHROMEOS

CHROMEOS macro is defined in third_party/webrtc.
This CL replaces it with more appropriate macro.

Bug: None
Change-Id: I38fd9e830b8d4b9a6585f7b554377e364daf50e8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2022024Reviewed-by: Owen Min <zmin@chromium.org>
Commit-Queue: Hiroki Sato <hirokisato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735657}

chrome/browser/enterprise_reporting/report_generator.cc

@@ -20,7 +20,7 @@
 #include "base/win/wmi.h"
 #endif
 
-#if defined(CHROMEOS)
+#if defined(OS_CHROMEOS)
 #include "chrome/browser/enterprise_reporting/android_app_info_generator.h"
 #include "chrome/browser/ui/app_list/arc/arc_app_list_prefs.h"
 #endif