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

chrome/browser/extensions/crx_installer.h

Index: chrome/browser/extensions/crx_installer.h
diff --git a/chrome/browser/extensions/crx_installer.h b/chrome/browser/extensions/crx_installer.h
index 1cf576ab2d0895979026743d6c1e2be3b2616b9f..43b54f2f40ba4ac34671287a99957ece66e951b9 100644
--- a/chrome/browser/extensions/crx_installer.h
+++ b/chrome/browser/extensions/crx_installer.h
@@ -133,8 +133,8 @@
   bool hash_check_failed() const { return hash_check_failed_; }
   void set_hash_check_failed(bool val) { hash_check_failed_ = val; }
 
-  void set_expected_version(const base::Version& val) {
-    expected_version_.reset(new base::Version(val));
+  void set_expected_version(const Version& val) {
+    expected_version_.reset(new Version(val));
     expected_version_strict_checking_ = true;
   }
 
@@ -326,7 +326,7 @@
   // installing.  Important for external sources, where claiming the wrong
   // version could cause unnecessary unpacking of an extension at every
   // restart.
-  scoped_ptr<base::Version> expected_version_;
+  scoped_ptr<Version> expected_version_;
 
   // If true, the actual version should be same with the |expected_version_|,
   // Otherwise the actual version should be equal to or newer than