[BUG] waitForNavigation does not work on headless despite it working in non-headless

[djasnowski]

Context:

• Playwright Version: 1.10.0
• Operating System: Linux OpenSUSE Leap 15.2
• Node.js version: 14.16.0
• Browser: Chromium

Code Snippet

Help us help you! Put down a short code snippet that illustrates your bug and
that we can run and debug locally. For example:

  test('can we export it to PDF?', async () => {
    const [popup] = await Promise.all([page?.waitForEvent('popup'), page.click('button:has-text("Export as PDF")')]);

    await popup.waitForNavigation({
      waitUntil: 'networkidle',
      timeout: 5000,
    });

    expect(await popup.url().startsWith('blob')).toBeTruthy();
  });

Describe the bug

Basically, this script clicks a button which opens a new tab with a blob:https://URL_EXAMPLE_OF_PDF of a PDF. When it's in non-headless mode, you can see it and it works. Tests pass. When it's in headless mode, the test fails like so:

    TimeoutError: page.waitForNavigation: Timeout 5000ms exceeded.
    =========================== logs ===========================
    waiting for navigation until "networkidle"
    ============================================================
    Note: use DEBUG=pw:api environment variable to capture Playwright logs.

      at node_modules/playwright/lib/client/waiter.js:49:51
      at Waiter.waitForPromise (node_modules/playwright/lib/client/waiter.js:57:28)
      at node_modules/playwright/lib/client/frame.js:120:36
      at Frame._wrapApiCall (node_modules/playwright/lib/client/channelOwner.js:77:28)

[mxschmitt]

Seems to be an duplicate of #6342 from my understanding. That the PDF won't lead to a PDF viewer on headless and trigger a download event instead.

[mxschmitt]

Closing for now as part of the triage. If the problem is still persistent, feel free to reopen.