Support --delete-old-versions in setup.exe.

chrome/installer/util/util_constants.cc

Index: chrome/installer/util/util_constants.cc
diff --git a/chrome/installer/util/util_constants.cc b/chrome/installer/util/util_constants.cc
index 91f2e8473a5ba5f06beb7963f9c96e9e04e1d21a..0ef53696e2a721ec4e504eb48fdcda99a35120c8 100644
--- a/chrome/installer/util/util_constants.cc
+++ b/chrome/installer/util/util_constants.cc
@@ -28,6 +28,10 @@ const char kConfigureUserSettings[] = "configure-user-settings";
 // in-use Chrome should be restarted ASAP.
 const char kCriticalUpdateVersion[] = "critical-update-version";
 
+// Delete files that belong to old versions of Chrome from the install
+// directory.
+const char kDeleteOldVersions[] = "delete-old-versions";
+
 // Delete user profile data. This param is useful only when specified with
 // kUninstall, otherwise it is silently ignored.
 const char kDeleteProfile[] = "delete-profile";