Context:

• Playwright Version: 1.8.1
• Operating System: Linux 5.4 KDE neon 5.21
• Node.js version: v14.15.5
• Browser: All
• Extra:

$ npx envinfo --preset playwright

  System:
    OS: Linux 5.4 KDE neon 5.21
    Memory: 3.68 GB / 15.56 GB
    Container: Yes
  Binaries:
    Node: 14.15.5 - /usr/bin/node
    Yarn: 1.22.5 - /usr/bin/yarn
    npm: 6.14.11 - /usr/bin/npm
  Languages:
    Bash: 5.0.17 - /usr/bin/bash
  npmPackages:
    playwright: 1.x => 1.8.1 

Code Snippet

"use strict";

import { chromium, firefox, webkit } from "playwright";

(async () => {
  const browser = await chromium.launch({
    headless: false,
    devtools: true,
  });
  const context = await browser.newContext();

  context.on("page", (page) => {
    page.on("requestfinished", (req) => {
      (async () => {
        const res = await req.response();

        if (res === null /* || 400 <= res?.status() */) {
          console.error(`No response returned at ${req.url()}`);
        }
      })();
    });
  });

  const page = await context.newPage();
  await page.goto("https://www.dropbox.com/login");
  await page.click(".auth-google");

  // await browser.close();
})();

Describe the bug

I'm trying to open a popup window and check if any requests failed.
As above code snippet, I add context.on("page", ...) event listener and attach page.on("requestfinished", ...) event listener when page is created.

However, in the requestfinished event of the HTML request (in the above code snippet, https://accounts.google.com/o/oauth2/auth/oauthchooseaccount...), await req.response() returns null.
I checked the browser window and devtools' console by adding headless: false and devtools: true option, but the HTML seems loaded properly.

I guess this happens only for the pages opened by the popup windows.