feat: restore Performance landing page

config/gni/devtools_grd_files.gni

@@ -1899,6 +1899,7 @@ grd_files_debug_sources = [
   "front_end/panels/timeline/LayoutShiftsTrackAppender.js",
   "front_end/panels/timeline/ModificationsManager.js",
   "front_end/panels/timeline/NetworkTrackAppender.js",
+  "front_end/panels/timeline/ReactNativeTimelineLandingPage.js",
   "front_end/panels/timeline/SaveFileFormatter.js",
   "front_end/panels/timeline/TargetForEvent.js",
   "front_end/panels/timeline/ThirdPartyTreeView.js",

front_end/panels/timeline/BUILD.gn

@@ -72,6 +72,7 @@ devtools_module("timeline") {
     "LayoutShiftsTrackAppender.ts",
     "ModificationsManager.ts",
     "NetworkTrackAppender.ts",
+    "ReactNativeTimelineLandingPage.ts",
     "SaveFileFormatter.ts",
     "TargetForEvent.ts",
     "ThirdPartyTreeView.ts",

front_end/panels/timeline/ReactNativeTimelineLandingPage.ts

@@ -0,0 +1,76 @@
+// Copyright (c) Meta Platforms, Inc. and affiliates.
+// Copyright 2024 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.
+
+import * as i18n from '../../core/i18n/i18n.js';
+import * as UI from '../../ui/legacy/legacy.js';
+
+const UIStrings = {
+    /**
+     * @description Text for an option to learn more about something
+     */
+    learnmore: 'Learn more',
+    /**
+     * @description Text in Timeline Panel of the Performance panel
+     */
+    wasd: 'WASD',
+    /**
+     * @description Text in Timeline Panel of the Performance panel
+     * @example {record} PH1
+     * @example {Ctrl + R} PH2
+     */
+    clickTheRecordButtonSOrHitSTo: 'Click the record button {PH1} or hit {PH2} to start a new recording.',
+    /**
+     * @description Text in Timeline Panel of the Performance panel
+     * @example {Ctrl + U} PH1
+     * @example {Learn more} PH2
+     */
+    afterRecordingSelectAnAreaOf:
+        'After recording, select an area of interest in the overview by dragging. Then, zoom and pan the timeline with the mousewheel or {PH1} keys. {PH2}',
+} as const;
+
+const str_ = i18n.i18n.registerUIStrings('panels/timeline/ReactNativeTimelineLandingPage.ts', UIStrings);
+const i18nString = i18n.i18n.getLocalizedString.bind(undefined, str_);
+
+export class ReactNativeTimelineLandingPage extends UI.Widget.VBox {
+    private readonly toggleRecordAction: UI.ActionRegistration.Action;
+
+    constructor(toggleRecordAction: UI.ActionRegistration.Action) {
+        super();
+
+        this.toggleRecordAction = toggleRecordAction;
+
+        this.contentElement.classList.add('timeline-landing-page', 'fill');
+        this.renderLegacyLandingPage();
+    }
+
+    private renderLegacyLandingPage(): void {
+        function encloseWithTag(tagName: string, contents: string): HTMLElement {
+            const e = document.createElement(tagName);
+            e.textContent = contents;
+            return e;
+        }
+
+        const learnMoreNode = UI.XLink.XLink.create(
+            'https://developer.chrome.com/docs/devtools/evaluate-performance/', i18nString(UIStrings.learnmore), undefined,
+            undefined, 'learn-more');
+
+        const recordKey = encloseWithTag(
+            'b',
+            UI.ShortcutRegistry.ShortcutRegistry.instance().shortcutsForAction('timeline.toggle-recording')[0].title());
+        const navigateNode = encloseWithTag('b', i18nString(UIStrings.wasd));
+
+        this.contentElement.classList.add('legacy');
+        const centered = this.contentElement.createChild('div');
+
+        const recordButton = UI.UIUtils.createInlineButton(UI.Toolbar.Toolbar.createActionButton(this.toggleRecordAction));
+
+        centered.createChild('p').appendChild(i18n.i18n.getFormatLocalizedString(
+            str_, UIStrings.clickTheRecordButtonSOrHitSTo, {PH1: recordButton, PH2: recordKey}));
+
+        centered.createChild('p').appendChild(i18n.i18n.getFormatLocalizedString(
+            str_, UIStrings.afterRecordingSelectAnAreaOf, {PH1: navigateNode, PH2: learnMoreNode}));
+    }
+}
+

front_end/panels/timeline/TimelinePanel.ts

@@ -65,6 +65,7 @@ import {Tracker} from './FreshRecording.js';
 import {IsolateSelector} from './IsolateSelector.js';
 import {AnnotationModifiedEvent, ModificationsManager} from './ModificationsManager.js';
 import * as Overlays from './overlays/overlays.js';
+import {ReactNativeTimelineLandingPage} from './ReactNativeTimelineLandingPage.js';
 import {cpuprofileJsonGenerator, traceJsonGenerator} from './SaveFileFormatter.js';
 import {type Client, TimelineController} from './TimelineController.js';
 import {Tab} from './TimelineDetailsView.js';
@@ -2250,9 +2251,13 @@ export class TimelinePanel extends UI.Panel.Panel implements Client, TimelineMod
       return;
     }
 
-    const liveMetrics = new TimelineComponents.LiveMetricsView.LiveMetricsView();
-    liveMetrics.isNode = isNode;
-    this.landingPage = LegacyWrapper.LegacyWrapper.legacyWrapper(UI.Widget.Widget, liveMetrics);
+    if (isReactNative) {
+      this.landingPage = new ReactNativeTimelineLandingPage(this.toggleRecordAction);
+    } else {
+      const liveMetrics = new TimelineComponents.LiveMetricsView.LiveMetricsView();
+      liveMetrics.isNode = isNode;
+      this.landingPage = LegacyWrapper.LegacyWrapper.legacyWrapper(UI.Widget.Widget, liveMetrics);
+    }
     this.landingPage.element.classList.add('timeline-landing-page', 'fill');
     this.landingPage.contentElement.classList.add('fill');
     this.landingPage.show(this.statusPaneContainer);

scripts/eslint_rules/lib/check-license-header.js

@@ -85,6 +85,7 @@ const META_CODE_PATHS = [
   'models/react_native',
   'panels/react_devtools',
   'panels/rn_welcome',
+  'panels/timeline/ReactNativeTimelineLandingPage.ts',
 ];
 
 const OTHER_LICENSE_HEADERS = [