New test cases for kiosk app crx file cache.

chrome/browser/chromeos/extensions/external_cache.h

Index: chrome/browser/chromeos/extensions/external_cache.h
diff --git a/chrome/browser/chromeos/extensions/external_cache.h b/chrome/browser/chromeos/extensions/external_cache.h
index 83834a05a1bbd13c0d1455f967533d32ce8b492d..4c0040e72f6f86c861a0e555957c9407c04778dc 100644
--- a/chrome/browser/chromeos/extensions/external_cache.h
+++ b/chrome/browser/chromeos/extensions/external_cache.h
@@ -120,6 +120,13 @@ class ExternalCache : public content::NotificationObserver,
   // files will be removed from disk too.
   void RemoveExtensions(const std::vector<std::string>& ids);
 
+  // If extension with |id| exists in the cache, returns |true|, |file_path| and
+  // |version| for the extension. Extension will be marked as used with current
+  // timestamp.
+  bool GetExtension(const std::string& id,
+                    base::FilePath* file_path,
+                    std::string* version);
+
  private:
   // Notifies the that the cache has been updated, providing
   // extensions loader with an updated list of extensions.