DevTools: add web audio context selector tests

This change adds basic tests that capture current behavior around the
Audio Context Selector.

It is meant as a start and not a complete list of tests,
more tests should be added in the future.

This also indirectly tests the UI.ListModel, UI.SoftDropDown, and
UI.ToolbarItem.

Change-Id: I7506c06e6cf8b865ab2645c9e9e4004df162e629
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1824060Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Hongchan Choi <hongchan@chromium.org>
Reviewed-by: Mandy Chen <mandy.chen@microsoft.com>
Commit-Queue: John Emau <John.Emau@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#704456}

third_party/blink/web_tests/http/tests/devtools/webaudio/audio-context-selector-test-expected.txt

+Tests the AudioContextSelector.
+
+Running: testStartsEmpty
+
+Number of contexts (items): 0
+Selected Context: null
+
+
+Running: testSelectsCreatedContext
+
+Number of contexts (items): 1
+Selected Context: {
+   "contextId": "924c4ee4-4cae-4e62-b4c6-71603edc39fd",
+   "contextType": "realtime"
+}
+
+
+Running: testResetClearsList
+
+Number of contexts (items): 0
+Selected Context: {
+   "contextId": "924c4ee4-4cae-4e62-b4c6-71603edc39fd",
+   "contextType": "realtime"
+}
+
+
+Running: testReSelectsCreatedContextAfterChange
+
+Number of contexts (items): 1
+Selected Context: {
+   "contextId": "924c4ee4-4cae-4e62-b4c6-71603edc39fd",
+   "contextType": "realtime"
+}
+
+
+Running: testFirstCreatedContextStaysSelected
+
+Number of contexts (items): 2
+Selected Context: {
+   "contextId": "924c4ee4-4cae-4e62-b4c6-71603edc39fd",
+   "contextType": "realtime"
+}
+
+
+Running: testChangingContextDoesNotChangeSelection
+
+Number of contexts (items): 2
+Selected Context: {
+   "contextId": "924c4ee4-4cae-4e62-b4c6-71603edc39fd",
+   "contextType": "realtime"
+}
+
+
+Running: testSelectedContextBecomesSelected
+
+Number of contexts (items): 2
+Selected Context: {
+   "contextId": "78a3e94e-4968-4bf6-8905-325109695c9e",
+   "contextType": "realtime"
+}
+
+
+Running: testOnListItemReplacedCalled
+_onListItemReplaced called with contexts (items) count: 1
+_onListItemReplaced called with contexts (items) count: 0
+_onListItemReplaced called with contexts (items) count: 1
+
+Number of contexts (items): 1
+Selected Context: {
+   "contextId": "924c4ee4-4cae-4e62-b4c6-71603edc39fd",
+   "contextType": "realtime"
+}
+
+

third_party/blink/web_tests/http/tests/devtools/webaudio/audio-context-selector-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() {
+  TestRunner.addResult(`Tests the AudioContextSelector.`);
+  await TestRunner.loadModule('web_audio');
+
+  /** @type {!Protocol.WebAudio.BaseAudioContext} */
+  const context1 = {
+    contextId: '924c4ee4-4cae-4e62-b4c6-71603edc39fd',
+    contextType: 'realtime'
+  };
+  /** @type {!Protocol.WebAudio.BaseAudioContext} */
+  const context2 = {
+    contextId: '78a3e94e-4968-4bf6-8905-325109695c9e',
+    contextType: 'realtime'
+  };
+
+  function dumpSelectorState(
+      /** @type {!WebAudio.AudioContextSelector} */ selector) {
+    TestRunner.addResult(`
+Number of contexts (items): ${selector._items.length}
+Selected Context: ${JSON.stringify(selector.selectedContext(), null, 3)}
+`);
+  }
+
+  TestRunner.runAsyncTestSuite([
+    async function testStartsEmpty() {
+      const selector = new WebAudio.AudioContextSelector();
+
+      dumpSelectorState(selector);
+    },
+
+    async function testSelectsCreatedContext() {
+      const selector = new WebAudio.AudioContextSelector();
+
+      selector.contextCreated({data: context1});
+
+      dumpSelectorState(selector);
+    },
+
+    async function testResetClearsList() {
+      const selector = new WebAudio.AudioContextSelector();
+
+      selector.contextCreated({data: context1});
+      selector.reset();
+
+      dumpSelectorState(selector);
+    },
+
+    async function testReSelectsCreatedContextAfterChange() {
+      const selector = new WebAudio.AudioContextSelector();
+
+      selector.contextCreated({data: context1});
+      selector.contextChanged({data: context1});
+
+      dumpSelectorState(selector);
+    },
+
+    async function testFirstCreatedContextStaysSelected() {
+      const selector = new WebAudio.AudioContextSelector();
+
+      selector.contextCreated({data: context1});
+      selector.contextCreated({data: context2});
+
+      dumpSelectorState(selector);
+    },
+
+    async function testChangingContextDoesNotChangeSelection() {
+      const selector = new WebAudio.AudioContextSelector();
+
+      selector.contextCreated({data: context1});
+      selector.contextCreated({data: context2});
+      selector.contextChanged({data: context2});
+
+      dumpSelectorState(selector);
+    },
+
+    async function testSelectedContextBecomesSelected() {
+      const selector = new WebAudio.AudioContextSelector();
+
+      selector.contextCreated({data: context1});
+      selector.contextCreated({data: context2});
+      selector.itemSelected(context2);
+
+      dumpSelectorState(selector);
+    },
+
+    async function testOnListItemReplacedCalled() {
+      function dumpItemCount() {
+        TestRunner.addResult(
+            `_onListItemReplaced called with contexts (items) count: ${
+                this._items.length}`);
+      }
+
+      TestRunner.addSniffer(
+          WebAudio.AudioContextSelector.prototype, '_onListItemReplaced',
+          dumpItemCount);
+
+      const selector = new WebAudio.AudioContextSelector();
+      selector.contextCreated({data: context1});
+      selector.contextChanged({data: context1});
+
+      dumpSelectorState(selector);
+    },
+  ]);
+})();
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