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

chrome/browser/extensions/extension_sync_data.cc

Index: chrome/browser/extensions/extension_sync_data.cc
diff --git a/chrome/browser/extensions/extension_sync_data.cc b/chrome/browser/extensions/extension_sync_data.cc
index af98c866df4911d78cf2a4a4980db07e10488bff..6404e8b61ca690b75f3cea42094aaf779b885019 100644
--- a/chrome/browser/extensions/extension_sync_data.cc
+++ b/chrome/browser/extensions/extension_sync_data.cc
@@ -236,7 +236,7 @@
     return false;
   }
 
-  base::Version specifics_version(specifics.version());
+  Version specifics_version(specifics.version());
   if (!specifics_version.IsValid()) {
     LOG(ERROR) << "Attempt to sync bad ExtensionSpecifics (bad version):\n"
                << GetExtensionSpecificsLogMessage(specifics);