Extensions and components should treat Lacros as 'cros'.

From the perspective of extensions, Lacros should be functionally
equivalent to ChromeOS rather than Linux.

Bug: 1164523
Change-Id: I020997a4185afb54018f19653f00f7b9d00f4f8c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2623121Reviewed-by: Joshua Pawlicki <waffles@chromium.org>
Commit-Queue: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#842605}

components/update_client/update_query_params.cc

@@ -32,9 +32,9 @@ const char kOs[] =
     "win";
 #elif defined(OS_ANDROID)
     "android";
-#elif BUILDFLAG(IS_CHROMEOS_ASH)
+#elif BUILDFLAG(IS_CHROMEOS_ASH) || BUILDFLAG(IS_CHROMEOS_LACROS)
     "cros";
-#elif defined(OS_LINUX) || BUILDFLAG(IS_CHROMEOS_LACROS)
+#elif defined(OS_LINUX)
     "linux";
 #elif defined(OS_FUCHSIA)
     "fuchsia";