third_party/WebKit/LayoutTests/http/tests/inspector-protocol/network/blocked-by-client-network-observer.js

(async function(testRunner) {
  var {page, session, dp} = await testRunner.startBlank(
      `Tests that 'BlockedByClient' network interception is executed with blockedReason set to 'inspector' (=devtools).`);

  await dp.Network.enable();
  await dp.Page.enable();
  await dp.Network.setRequestInterception({
    patterns: [{ urlPattern: '*' }]
  });
  dp.Network.onRequestIntercepted(event => {
    const url = event.params.request.url;
    if (url.endsWith('page-with-subresource.html')) {
      testRunner.log(`continuing to load ${url}`);
      dp.Network.continueInterceptedRequest({
        interceptionId: event.params.interceptionId,
      });
    } else {
      testRunner.log(`blocking ${url}`);
      dp.Network.continueInterceptedRequest({
        interceptionId: event.params.interceptionId,
        errorReason: 'BlockedByClient'
      });
    }
  });

  // We map the requestIds to URLs since these are stable within this test.
  // Also this shows both the requests that we're blocking and the ones that
  // continue.
  const urlByRequestId = new Map();
  dp.Network.onRequestWillBeSent(event => {
    const requestId = event.params.requestId;
    const url = event.params.request.url;
    testRunner.log(`request will be sent for ${url}`);
    urlByRequestId.set(event.params.requestId, event.params.request.url);
  });

  // Log the requests that are blocked, with the blockedReason indicating
  // that they were blocked via the devtools protocol (inspector).
  dp.Network.onLoadingFailed(event => {
    const url = urlByRequestId.get(event.params.requestId);
    const blockedReason = event.params.blockedReason;
    testRunner.log(`loading failed for ${url}: blockedReason = ${blockedReason}`);
  });

  await dp.Runtime.enable();
  // Test blocking a page. This page doesn't exist so it would 404 but that's
  // OK because the interception / blocking happens before any network fetch
  // would take place anyway.
  await page.navigate('./resources/to-be-blocked.html');
  // This page will not be blocked so it just passes through in the interception.
  // The resource exists, and references to-be-blocked.jpg, a subresource.
  await page.navigate('./resources/page-with-subresource.html');
  testRunner.completeTest();
})