Enable side-by-side beta and dev channels.

chrome/install_static/google_chrome_install_modes.h

Index: chrome/install_static/google_chrome_install_modes.h
diff --git a/chrome/install_static/google_chrome_install_modes.h b/chrome/install_static/google_chrome_install_modes.h
index 700a132bb64992e40bdf1ece17e946e4808286ed..66838c3b4ca293b7899b850140a893f6ab3e1dfa 100644
--- a/chrome/install_static/google_chrome_install_modes.h
+++ b/chrome/install_static/google_chrome_install_modes.h
@@ -17,6 +17,8 @@ enum : bool {
 // resource strings in chrome/installer/util/prebuild/create_string_rc.
 enum InstallConstantIndex {
   STABLE_INDEX,
+  BETA_INDEX,
+  DEV_INDEX,
   CANARY_INDEX,
   NUM_INSTALL_MODES,
 };