Support rollback with installerdata in mini_installer

chrome/installer/util/util_constants.h

Index: chrome/installer/util/util_constants.h
diff --git a/chrome/installer/util/util_constants.h b/chrome/installer/util/util_constants.h
index 13c905d8b84a7c30785221f34836bfeb920bc8dc..59151c35605f0118c9ec0dadee9aba65cd3376ca 100644
--- a/chrome/installer/util/util_constants.h
+++ b/chrome/installer/util/util_constants.h
@@ -88,8 +88,12 @@ enum InstallStatus {
   REENABLE_UPDATES_FAILED = 56,  // Autoupdates could not be enabled.
   UNPACKING_FAILED     = 57,  // Unpacking the (possibly patched) uncompressed
                               // archive failed.
+  IN_USE_DOWNGRADE     = 58,  // Successfully downgrade chrome but current

[grt (UTC plus 2), 2016/04/28 16:55:30]

please add these to InstallStatus enum in
tools/metrics/histograms/histograms.xml

[zmin, 2016/04/28 17:51:29]

Done.

+                              // version is still running.
+  OLD_VERSION_DOWNGRADE = 59,  // Successfully downgrade chrome to an older
+                               // version.
 
-  MAX_INSTALL_STATUS = 58,    // Bump this out to make space for new results.
+  MAX_INSTALL_STATUS   = 60,  // Bump this out to make space for new results.
 };
 
 // The type of an update archive.