Revert of Delete old files after an update.

chrome/installer/util/installer_state.h

Index: chrome/installer/util/installer_state.h
diff --git a/chrome/installer/util/installer_state.h b/chrome/installer/util/installer_state.h
index 1de3000b8fae674bc737d71184a4059c059ffb64..2b624659c56b5e04cb7b4d43e2e0a2c7d76e7b6e 100644
--- a/chrome/installer/util/installer_state.h
+++ b/chrome/installer/util/installer_state.h
@@ -7,6 +7,7 @@
 
 #include <stdint.h>
 
+#include <set>
 #include <string>
 #include <vector>
 
@@ -177,6 +178,13 @@
   // (for example <target_path>\Google\Chrome\Application\<Version>\Installer)
   base::FilePath GetInstallerDirectory(const base::Version& version) const;
 
+  // Try to delete all directories under |temp_path| whose versions are less
+  // than |new_version| and not equal to |existing_version|. |existing_version|
+  // may be NULL.
+  void RemoveOldVersionDirectories(const base::Version& new_version,
+                                   base::Version* existing_version,
+                                   const base::FilePath& temp_path) const;
+
   // Adds to |com_dll_list| the list of COM DLLs that are to be registered
   // and/or unregistered. The list may be empty.
   void AddComDllList(std::vector<base::FilePath>* com_dll_list) const;
@@ -235,6 +243,11 @@
   bool IsMultiInstallUpdate(const MasterPreferences& prefs,
                             const InstallationState& machine_state);
 
+  // Enumerates all files named one of
+  // [chrome.exe, old_chrome.exe, new_chrome.exe] in target_path_ and
+  // returns their version numbers in a set.
+  void GetExistingExeVersions(std::set<std::string>* existing_versions) const;
+
   // Sets this object's level and updates the root_key_ accordingly.
   void set_level(Level level);