DevTools: Add axe a11y test for javascript breakpoints pane

This CL adds an axe test for the Sources panel javascript breakpoints
pane.

Bug: 963183
Change-Id: I386ccb516ed96bf276c70fcf5a813d4c5819d5e8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1650322Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Jack Lynch <jalyn@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#703947}

third_party/blink/web_tests/http/tests/devtools/a11y-axe-core/sources/javascript-breakpoints-a11y-test-expected.txt

+Testing accessibility in the javascript breakpoints pane.
+Setting a breakpoint.
+Running axe on the javascript breakpoints pane.
+aXe violations: []
+
+

third_party/blink/web_tests/http/tests/devtools/a11y-axe-core/sources/javascript-breakpoints-a11y-test.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() {
+  await TestRunner.loadModule('axe_core_test_runner');
+  await TestRunner.loadModule('sources_test_runner');
+
+  TestRunner.addResult('Testing accessibility in the javascript breakpoints pane.');
+  await SourcesTestRunner.startDebuggerTestPromise(true);
+  await TestRunner.navigatePromise('../../sources/debugger/resources/set-breakpoint.html');
+  const sourceFrame = await SourcesTestRunner.showScriptSourcePromise('set-breakpoint.html');
+
+  TestRunner.addResult('Setting a breakpoint.');
+  await SourcesTestRunner.createNewBreakpoint(sourceFrame, 13, '', true)
+  await SourcesTestRunner.createNewBreakpoint(sourceFrame, 11, '', false)
+  await UI.viewManager.showView('sources.jsBreakpoints');
+  const breakpointsPaneElement = runtime.sharedInstance(Sources.JavaScriptBreakpointsSidebarPane).contentElement;
+
+  TestRunner.addResult('Running axe on the javascript breakpoints pane.');
+  await AxeCoreTestRunner.runValidation(breakpointsPaneElement);
+  SourcesTestRunner.completeDebuggerTest();
+})();