When opening the Devtools, screen, the loading of DevTools itself is slow

When opening the Devtools, screen, the loading of DevTools itself is slow. The loading of DevTools takes places in an .

DevTools should be pre-loaded within the iframe, or somehow preloaded/initialized, so the loading is close to instant.

Start by tracing where the DevTools iframe is created and loaded, then measure the current delay when opening the DevTools screen. The work is done when DevTools is preloaded or initialized early enough that opening the screen is close to instant, with the relevant loading behavior verified.

Written by the indexing model from the issue text.