List all header files as part of //components/prefs sources on iOS.

The files were excluded from sources on iOS but they were directly
or indirectly used by iOS code. Since there is no technicall reason
to prevent iOS from including those headers, remove the conditional
when adding them to sources.

BUG=None

Review-Url: https://codereview.chromium.org/2517533002
Cr-Commit-Position: refs/heads/master@{#433317}

components/prefs/BUILD.gn

@@ -4,6 +4,7 @@
 
 component("prefs") {
   sources = [
+    "base_prefs_export.h",
     "command_line_pref_store.cc",
     "command_line_pref_store.h",
     "default_pref_store.cc",
@@ -14,12 +15,16 @@ component("prefs") {
     "json_pref_store.h",
     "overlay_user_pref_store.cc",
     "overlay_user_pref_store.h",
+    "persistent_pref_store.h",
     "pref_change_registrar.cc",
     "pref_change_registrar.h",
+    "pref_filter.h",
     "pref_member.cc",
     "pref_member.h",
+    "pref_notifier.h",
     "pref_notifier_impl.cc",
     "pref_notifier_impl.h",
+    "pref_observer.h",
     "pref_registry.cc",
     "pref_registry.h",
     "pref_registry_simple.cc",
@@ -38,17 +43,8 @@ component("prefs") {
     "scoped_user_pref_update.h",
     "value_map_pref_store.cc",
     "value_map_pref_store.h",
+    "writeable_pref_store.h",
   ]
-  if (!is_ios) {
-    sources += [
-      "base_prefs_export.h",
-      "persistent_pref_store.h",
-      "pref_filter.h",
-      "pref_notifier.h",
-      "pref_observer.h",
-      "writeable_pref_store.h",
-    ]
-  }
 
   defines = [ "COMPONENTS_PREFS_IMPLEMENTATION" ]