Add ARC version to help and version pages

chromeos/system/version_loader.h

Index: chromeos/system/version_loader.h
diff --git a/chromeos/system/version_loader.h b/chromeos/system/version_loader.h
index 7981dc2830ac9d0c88013b490ba6806aa81d9d31..de6d2d73dedddce66cf34cd288a348f6286125dc 100644
--- a/chromeos/system/version_loader.h
+++ b/chromeos/system/version_loader.h
@@ -24,6 +24,10 @@ enum VersionFormat {
 // Must be run on a blocking thread pool.
 CHROMEOS_EXPORT std::string GetVersion(VersionFormat format);
 
+// Gets the ARC version.
+// Must be run on a blocking thread pool.
+CHROMEOS_EXPORT std::string GetARCVersion();
+
 // Gets the firmware info.
 // Must be run on a blocking thread pool.
 CHROMEOS_EXPORT std::string GetFirmware();