Get rid of the extension's "Current Version" file.

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 d7ae5047a9dd3d99871b311a78198917d6b067db..c1a4d55ffcd386279a663abcc2443c932351b18d 100644
--- a/chrome/browser/extensions/crx_installer.h
+++ b/chrome/browser/extensions/crx_installer.h
@@ -138,6 +138,10 @@ class CrxInstaller :
   // ExtensionsService on success, or delete it on failure.
   scoped_ptr<Extension> extension_;
 
+  // If non-empty, contains the current version of the extension we're
+  // installing (for upgrades).
+  std::string current_version_;
+
   // The icon we will display in the installation UI, if any.
   scoped_ptr<SkBitmap> install_icon_;