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

chrome/browser/extensions/crx_installer.cc

Index: chrome/browser/extensions/crx_installer.cc
diff --git a/chrome/browser/extensions/crx_installer.cc b/chrome/browser/extensions/crx_installer.cc
index 4899cf2ab14e5166cbd47e75f1990270a42113e9..2effb1afb6afdec33265efc406e46631acc31ed5 100644
--- a/chrome/browser/extensions/crx_installer.cc
+++ b/chrome/browser/extensions/crx_installer.cc
@@ -154,7 +154,7 @@
     expected_id_ = approval->extension_id;
   }
   if (approval->minimum_version.get()) {
-    expected_version_.reset(new base::Version(*approval->minimum_version));
+    expected_version_.reset(new Version(*approval->minimum_version));
     expected_version_strict_checking_ = false;
   }
 
@@ -483,7 +483,7 @@
         SharedModuleInfo::GetImports(extension());
     std::vector<SharedModuleInfo::ImportInfo>::const_iterator i;
     for (i = imports.begin(); i != imports.end(); ++i) {
-      base::Version version_required(i->minimum_version);
+      Version version_required(i->minimum_version);
       const Extension* imported_module =
           service->GetExtensionById(i->extension_id, true);
       if (imported_module &&
@@ -684,7 +684,7 @@
   DCHECK(installer_task_runner_->RunsTasksOnCurrentThread());
 
   if (!current_version_.empty()) {
-    base::Version current_version(current_version_);
+    Version current_version(current_version_);
     if (current_version.CompareTo(*(extension()->version())) > 0) {
       ReportFailureFromFileThread(CrxInstallError(
           CrxInstallError::ERROR_DECLINED,