[Devtools] Add test for uncovered css files

This patch adds a test to check that all loaded css files are shown
in the coverage list view even when not (yet) covered at all.

Fixed: chromium:949045
Change-Id: Idda4df73866590010d59f84cd4193c051fe1cc0c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1903359Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Jan Scheffler <janscheffler@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715220}

third_party/blink/web_tests/http/tests/devtools/coverage/coverage-view-unused-expected.txt

+Test if coverage view also shows completly uncovered css files
+
+Make sure all files are shown even when not covered so far
+.../devtools/coverage/resources/not-initially-used.css CSS used: 0 unused: 24 total: 24
+.../devtools/coverage/resources/unused.css CSS used: 0 unused: 22 total: 22
+.../devtools/coverage/resources/used.css CSS used: 24 unused: 0 total: 24
+.../devtools/coverage/resources/empty.css CSS used: 0 unused: 0 total: 0
+Make sure files are added as they are loaded on reload
+Page reloaded.
+.../devtools/coverage/resources/unused-css-coverage.html JS (per block) used: 7 unused: 275 total: 282
+.../devtools/coverage/resources/not-initially-used.css CSS used: 0 unused: 24 total: 24
+.../devtools/coverage/resources/unused.css CSS used: 0 unused: 22 total: 22
+.../devtools/coverage/resources/used.css CSS used: 24 unused: 0 total: 24
+.../devtools/coverage/resources/empty.css CSS used: 0 unused: 0 total: 0
+Make sure files are added when they are not part of the initial load
+.../devtools/coverage/resources/unused-css-coverage.html JS (per block) used: 143 unused: 139 total: 282
+.../devtools/coverage/resources/not-initially-used.css CSS used: 0 unused: 24 total: 24
+.../devtools/coverage/resources/unused.css CSS used: 0 unused: 22 total: 22
+.../devtools/coverage/resources/used.css CSS used: 24 unused: 0 total: 24
+.../devtools/coverage/resources/empty.css CSS used: 0 unused: 0 total: 0
+Make sure coverage gets updated if anything changes
+.../devtools/coverage/resources/unused.css CSS used: 0 unused: 22 total: 22
+.../devtools/coverage/resources/used.css CSS used: 24 unused: 0 total: 24
+.../devtools/coverage/resources/unused-css-coverage.html JS (per block) used: 282 unused: 0 total: 282
+.../devtools/coverage/resources/not-initially-used.css CSS used: 24 unused: 0 total: 24
+.../devtools/coverage/resources/empty.css CSS used: 0 unused: 0 total: 0
+

third_party/blink/web_tests/http/tests/devtools/coverage/coverage-view-unused.js

+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+(async function() {
+  TestRunner.addResult(`Test if coverage view also shows completly uncovered css files\n`);
+  await TestRunner.loadModule('coverage_test_runner');
+  await TestRunner.navigatePromise(TestRunner.url('resources/unused-css-coverage.html'));
+
+  await CoverageTestRunner.startCoverage(true);
+
+  TestRunner.addResult('Make sure all files are shown even when not covered so far');
+  await CoverageTestRunner.pollCoverage();
+  CoverageTestRunner.dumpCoverageListView();
+
+  TestRunner.addResult('Make sure files are added as they are loaded on reload');
+  await TestRunner.reloadPagePromise();
+  await CoverageTestRunner.pollCoverage();
+  CoverageTestRunner.dumpCoverageListView();
+
+  TestRunner.addResult('Make sure files are added when they are not part of the initial load');
+  await TestRunner.evaluateInPagePromise('appendStylesheet()');
+  await CoverageTestRunner.pollCoverage();
+  CoverageTestRunner.dumpCoverageListView();
+
+  TestRunner.addResult('Make sure coverage gets updated if anything changes');
+  await TestRunner.evaluateInPagePromise('appendElement()');
+  await CoverageTestRunner.pollCoverage();
+  CoverageTestRunner.dumpCoverageListView();
+
+  await CoverageTestRunner.stopCoverage();
+  TestRunner.completeTest();
+})();

third_party/blink/web_tests/http/tests/devtools/coverage/resources/not-initially-used.css

+h2 {
+    color: green;
+}
\ No newline at end of file

third_party/blink/web_tests/http/tests/devtools/coverage/resources/unused-css-coverage.html

+<html>
+<link rel="stylesheet" href="used.css" />
+<link rel="stylesheet" href="not-initially-used.css" />
+<link rel="stylesheet" href="unused.css" />
+<link rel="stylesheet" href="empty.css" />
+<script>
+  function appendStylesheet() {
+    document.body.innerAdjecentHTML('afterend', '<link rel="stylesheet" href="lazily-loaded.css" />');
+  }
+  function appendElement() {
+    const e = document.createElement('h2');
+    e.innerText = 'This is a test';
+    document.body.append(e);
+  }
+</script>
+<body>
+  <h1>Hello World</h1>
+</body>
+</html>

third_party/blink/web_tests/http/tests/devtools/coverage/resources/unused.css

+h3{
+    color: blue;
+}
\ No newline at end of file

third_party/blink/web_tests/http/tests/devtools/coverage/resources/used.css

+body {
+    color: red;
+}
\ No newline at end of file