Remove non-chromeos support from src/ash BUILD.gn files

ash/common/strings/BUILD.gn

Index: ash/common/strings/BUILD.gn
diff --git a/ash/common/strings/BUILD.gn b/ash/common/strings/BUILD.gn
index 8ca655ab8bd2df6f13ecfc568c357bf7552e618e..207c4e2ffb36e89df1a7309ffca59c1d8eb408a6 100644
--- a/ash/common/strings/BUILD.gn
+++ b/ash/common/strings/BUILD.gn
@@ -5,6 +5,8 @@
 import("//tools/grit/grit_rule.gni")
 import("//tools/grit/repack.gni")
 
+assert(is_chromeos)
+
 grit("strings") {
   source = "../../ash_strings.grd"
   outputs = [
@@ -75,26 +77,19 @@ template("repack_one_locale_ash") {
     # Each input pak file should also have a deps line for completeness.
     sources = [
       "$root_gen_dir/ash/common/strings/ash_strings_${locale}.pak",
+      "$root_gen_dir/device/bluetooth/strings/bluetooth_strings_${locale}.pak",
+      "$root_gen_dir/ui/chromeos/strings/ui_chromeos_strings_${locale}.pak",
       "$root_gen_dir/ui/strings/app_locale_settings_${locale}.pak",
       "$root_gen_dir/ui/strings/ui_strings_${locale}.pak",
     ]
 
     deps = [
       "//ash/common/strings",
+      "//device/bluetooth/strings",
+      "//ui/chromeos/strings",
       "//ui/strings:app_locale_settings",
       "//ui/strings:ui_strings",
     ]
-
-    if (is_chromeos) {
-      sources += [
-        "$root_gen_dir/device/bluetooth/strings/bluetooth_strings_${locale}.pak",
-        "$root_gen_dir/ui/chromeos/strings/ui_chromeos_strings_${locale}.pak",
-      ]
-      deps += [
-        "//device/bluetooth/strings",
-        "//ui/chromeos/strings",
-      ]
-    }
   }
 }