[BUG] page.waitForLoadState(networkidle times out with nested iframes

[k15a]

Context:

• Playwright Version: 1.0.2
• Operating System: Mac
• Node version: v12.16.3
• Browser: Chromium

Code Snippet

Reproduction is here: https://github.com/k15a/pw-site-isolation-wait-for-bug

Describe the bug

If there are two nested iframe that run on different origins (index.html -> https://domain1.com/iframe.html -> https://domain2.com/iframe.html) page.waitForLoadState

[k15a]

No idea where this issues comes from...
Correct issue: #2258