Revert of base: Remove using:: declaration from version.h header.

chrome/installer/setup/setup_main.cc

Index: chrome/installer/setup/setup_main.cc
diff --git a/chrome/installer/setup/setup_main.cc b/chrome/installer/setup/setup_main.cc
index f288649f33939537e24817d319bd21e9fc615aa8..8bdd55c692be09e778be8c91a01c76bf38409fd8 100644
--- a/chrome/installer/setup/setup_main.cc
+++ b/chrome/installer/setup/setup_main.cc
@@ -894,7 +894,7 @@
     scoped_ptr<WorkItemList> delegate_execute_list(
         WorkItem::CreateWorkItemList());
     installer::AddDelegateExecuteWorkItems(
-        installer_state, chrome_exe.DirName(), base::Version(), chrome,
+        installer_state, chrome_exe.DirName(), Version(), chrome,
         delegate_execute_list.get());
     delegate_execute_list->Do();
     if (ShellUtil::CanMakeChromeDefaultUnattended()) {
@@ -1125,7 +1125,7 @@
       BrowserDistribution* browser_dist = product.distribution();
       // We started as system-level and have been re-launched as user level
       // to continue with the toast experiment.
-      base::Version installed_version;
+      Version installed_version;
       InstallUtil::GetChromeVersion(browser_dist, true, &installed_version);
       if (!installed_version.IsValid()) {
         LOG(ERROR) << "No installation of "
@@ -1389,8 +1389,9 @@
   }
 
   VLOG(1) << "unpacked to " << unpack_path.value();
-  base::FilePath src_path(unpack_path.Append(kInstallSourceChromeDir));
-  scoped_ptr<base::Version>
+  base::FilePath src_path(
+      unpack_path.Append(kInstallSourceChromeDir));
+  scoped_ptr<Version>
       installer_version(GetMaxVersionFromArchiveDir(src_path));
   if (!installer_version.get()) {
     LOG(ERROR) << "Did not find any valid version in installer.";