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

chrome/browser/extensions/extension_prefs.h

Index: chrome/browser/extensions/extension_prefs.h
diff --git a/chrome/browser/extensions/extension_prefs.h b/chrome/browser/extensions/extension_prefs.h
index 291556c79b482cd8db487a623b33d2ec47622c67..59adfd87de9e0aba24531e4be1d73dcd5e589638 100644
--- a/chrome/browser/extensions/extension_prefs.h
+++ b/chrome/browser/extensions/extension_prefs.h
@@ -49,6 +49,13 @@ class ExtensionPrefs {
   // Called to change the extension's state when it is enabled/disabled.
   void SetExtensionState(Extension* extension, Extension::State);
 
+  // Returns the version string for the currently installed extension, or
+  // the empty string if not found.
+  std::string GetVersionString(const std::string& extension_id);
+
+  // Ensure old extensions have fully up-to-date prefs values.
+  void MigrateToPrefs(Extension* extension);
+
   // Returns base extensions install directory.
   const FilePath& install_directory() const { return install_directory_; }
 
@@ -106,19 +113,16 @@ class InstalledExtensions {
   explicit InstalledExtensions(ExtensionPrefs* prefs);
   ~InstalledExtensions();
 
-  typedef Callback3<const std::string&,
+  typedef Callback4<DictionaryValue*,
+                    const std::string&,
                     const FilePath&,
                     Extension::Location>::Type Callback;
 
   // Runs |callback| for each installed extension with the path to the
   // version directory and the location. Blacklisted extensions won't trigger
-  // the callback.
+  // the callback. Ownership of |callback| is transferred to callee.
   void VisitInstalledExtensions(Callback *callback);
 
-  // Same as above, but only for the given extension.
-  void VisitInstalledExtension(const std::string& extension_id,
-                               Callback *callback);
-
  private:
   // A copy of the extensions pref dictionary so that this can be passed
   // around without a dependency on prefs.