Support rollback with installerdata in mini_installer

chrome/installer/setup/setup_util.cc

Index: chrome/installer/setup/setup_util.cc
diff --git a/chrome/installer/setup/setup_util.cc b/chrome/installer/setup/setup_util.cc
index 93826c86ad0c1409b7639320db0e7341c990d2e2..30fb51d9d53cbb5e8ebd349a1340a4eadc0ae464 100644
--- a/chrome/installer/setup/setup_util.cc
+++ b/chrome/installer/setup/setup_util.cc
@@ -12,6 +12,7 @@
 #include <algorithm>
 #include <iterator>
 #include <set>
+#include <string>
 
 #include "base/command_line.h"
 #include "base/cpu.h"
@@ -31,6 +32,8 @@
 #include "chrome/installer/util/google_update_constants.h"
 #include "chrome/installer/util/installation_state.h"
 #include "chrome/installer/util/installer_state.h"
+#include "chrome/installer/util/master_preferences.h"
+#include "chrome/installer/util/master_preferences_constants.h"
 #include "chrome/installer/util/util_constants.h"
 #include "courgette/courgette.h"
 #include "courgette/third_party/bsdiff.h"
@@ -540,6 +543,12 @@ base::string16 GuidToSquid(const base::string16& guid) {
   return squid;
 }
 
+bool IsRollbackEnabled(const MasterPreferences& prefs) {
+  std::string rollback_flag = "";

[Georges Khalil, 2016/04/27 12:38:02]

Should we always return false for non msi installs?

[zmin, 2016/04/27 15:20:18]

The rollback flag is stored in the installer data which is same as msi flag.
Anyone wants to rollback Chrome with mini_installer can simply change both flags
together. Here is a sample of installer data:

{"distribution":{"msi":false,"system_level":false,...,"rollback":"Enable"}}

[Georges Khalil, 2016/04/28 14:36:30]

Gotcha.

+  prefs.GetString(master_preferences::kRollback, &rollback_flag);
+  return rollback_flag == master_preferences::kRollbackEnable;
+}
+
 ScopedTokenPrivilege::ScopedTokenPrivilege(const wchar_t* privilege_name)
     : is_enabled_(false) {
   HANDLE temp_handle;