Force migrate all clients from multi-install back to single-install.

chrome/installer/mini_installer/regkey.h

Index: chrome/installer/mini_installer/regkey.h
diff --git a/chrome/installer/mini_installer/regkey.h b/chrome/installer/mini_installer/regkey.h
index f323b7c697fe69bb3c9f355c0098b4220ee99fba..86dbf8b17475e3a3c1fd368f20cb0e246f2c4eb4 100644
--- a/chrome/installer/mini_installer/regkey.h
+++ b/chrome/installer/mini_installer/regkey.h
@@ -55,11 +55,19 @@ class RegKey {
   HKEY key_;
 };  // class RegKey
 
-
-// Helper function to get the RegKey associated with the "client state" of
-// the given |app_guid|.
-bool OpenClientStateKey(HKEY root_key, const wchar_t* app_guid,
-                        REGSAM access, RegKey* key);
+// Initializes |key| with the desired |access| to |app_guid|'s Clients key.
+// Returns ERROR_SUCCESS on success, or a Windows error code on failure.
+LONG OpenClientsKey(HKEY root_key,
+                    const wchar_t* app_guid,
+                    REGSAM access,
+                    RegKey* key);
+
+// Initializes |key| with the desired |access| to |app_guid|'s ClientState key.
+// Returns ERROR_SUCCESS on success, or a Windows error code on failure.
+LONG OpenClientStateKey(HKEY root_key,
+                        const wchar_t* app_guid,
+                        REGSAM access,
+                        RegKey* key);
 
 }  // namespace mini_installer