Remove RuntimeAPIDelegate::GetPreviousVersion.

extensions/browser/api/runtime/runtime_api_delegate.h

Index: extensions/browser/api/runtime/runtime_api_delegate.h
diff --git a/extensions/browser/api/runtime/runtime_api_delegate.h b/extensions/browser/api/runtime/runtime_api_delegate.h
index f0ac21c4ae848f305cb65dac30ea4cb9f32e9151..e194d32db8f30076f411223f9166af956b61f23d 100644
--- a/extensions/browser/api/runtime/runtime_api_delegate.h
+++ b/extensions/browser/api/runtime/runtime_api_delegate.h
@@ -51,10 +51,6 @@ class RuntimeAPIDelegate {
   // Unregisters an UpdateObserver on behalf of the runtime API.
   virtual void RemoveUpdateObserver(UpdateObserver* observer) = 0;
 
-  // Determines an extension's previously installed version if applicable.
-  virtual base::Version GetPreviousExtensionVersion(
-      const Extension* extension) = 0;
-
   // Reloads an extension.
   virtual void ReloadExtension(const std::string& extension_id) = 0;