ui: Deprecate 'enableScrollJankPluginV2' flag

- Remove enableScrollJankPluginV2 flag.
- Remove ChromeScrollJank from the list of default plugins.
- Add a little patch that runs on start up and ensures anyone with the
enableScrollJankPlugin flag set has the ChromeScrollJank plugin auto
enabled. This patch only needs to run once, and will be removed after
a few weeks/months.

Change-Id: Ica67c3ca80e95bfd1e27f626446569842f5a4937

ui/src/core/default_plugins.ts

@@ -43,7 +43,6 @@ export const defaultPlugins = [
  'perfetto.AndroidLog',
  'perfetto.Annotation',
  'perfetto.AsyncSlices',
- 'perfetto.ChromeScrollJank',
  'perfetto.CoreCommands',
  'perfetto.Counter',
  'perfetto.CpuFreq',

ui/src/core/feature_flags.ts

@@ -118,6 +118,21 @@ class Flags {
 
  this.store.save(this.overrides);
  }
+
+ /**
+ * Modify an override at runtime and save it back to local storage.
+ *
+ * This method operates on the raw JSON in local storage and doesn't require
+ * the presence of a flag to work. Thus, it may be called at any point in the
+ * lifecycle of the flags object.
+ *
+ * @param key - The key of the flag to modify.
+ * @param state - The desired state of the flag override.
+ */
+ patchOverride(key: string, state: OverrideState): void {
+ this.overrides[key] = state;
+ this.save();
+ }
 }
 
 export interface Flag {

ui/src/core_plugins/chrome_scroll_jank/index.ts

@@ -14,7 +14,6 @@
 
 import {uuidv4Sql} from '../../base/uuid';
 import {generateSqlWithInternalLayout} from '../../common/internal_layout_utils';
-import {featureFlags} from '../../core/feature_flags';
 import {Trace} from '../../public/trace';
 import {PerfettoPlugin, PluginDescriptor} from '../../public/plugin';
 import {EventLatencySliceDetailsPanel} from './event_latency_details_panel';
@@ -25,29 +24,60 @@ import {ScrollJankV3Track} from './scroll_jank_v3_track';
 import {TopLevelScrollTrack} from './scroll_track';
 import {ScrollJankCauseMap} from './scroll_jank_cause_map';
 import {TrackNode} from '../../public/workspace';
+import {featureFlags, OverrideState} from '../../core/feature_flags';
 
-const ENABLE_SCROLL_JANK_PLUGIN_V2 = featureFlags.register({
- id: 'enableScrollJankPluginV2',
- name: 'Enable Chrome Scroll Jank plugin V2',
- description: 'Adds new tracks and visualizations for scroll jank.',
- defaultValue: false,
-});
+// Before plugins were a thing, this plugin was enabled using a feature flag.
+// However, nowadays, plugins themselves can be selectively enabled and
+// disabled. This function inspects local storage to see whether the old feature
+// flag is enabled, and patches the flags settings to enable the chrome scroll
+// jank plugin, before deleting the old flag. This provides a seamless
+// experience for anyone who currently uses the chrome scroll jank plugin.
+//
+// TODO(stevegolton): Remove this code after 2025-01-01. This should give it
+// enough time on stable for most relevant users to have run it at least once.
+function patchChromeScrollJankFlag() {
+ try {
+ const flagsKey = 'perfettoFeatureFlags';
+ const enableScrollJankPluginV2FlagKey = 'enableScrollJankPluginV2';
+ const chromeScrollJankPuginFlagKey = 'plugin_perfetto.ChromeScrollJank';
+
+ const flagsRaw = localStorage.getItem(flagsKey);
+ if (flagsRaw) {
+ const flags = JSON.parse(flagsRaw);
+ if (flags[enableScrollJankPluginV2FlagKey] === 'OVERRIDE_TRUE') {
+ featureFlags.patchOverride(
+ chromeScrollJankPuginFlagKey,
+ OverrideState.TRUE,
+ );
+ console.log(
+ `Cleared deprecated 'enableScrollJankPluginV2' flag & enabled 'ChromeScrollJank' plugin.`,
+ );
+ }
+
+ // Just remove the original flag
+ delete flags[enableScrollJankPluginV2FlagKey];
+ localStorage.setItem(flagsKey, JSON.stringify(flags));
+ }
+ } catch {
+ // Ignore - this was very much best-effort.
+ }
+}
+
+patchChromeScrollJankFlag();
 
 class ChromeScrollJankPlugin implements PerfettoPlugin {
  async onTraceLoad(ctx: Trace): Promise<void> {
- if (ENABLE_SCROLL_JANK_PLUGIN_V2.get()) {
- const group = new TrackNode({
- title: 'Chrome Scroll Jank',
- sortOrder: -30,
- isSummary: true,
- });
- await this.addTopLevelScrollTrack(ctx, group);
- await this.addEventLatencyTrack(ctx, group);
- await this.addScrollJankV3ScrollTrack(ctx, group);
- await ScrollJankCauseMap.initialize(ctx.engine);
- ctx.workspace.addChildInOrder(group);
- group.expand();
- }
+ const group = new TrackNode({
+ title: 'Chrome Scroll Jank',
+ sortOrder: -30,
+ isSummary: true,
+ });
+ await this.addTopLevelScrollTrack(ctx, group);
+ await this.addEventLatencyTrack(ctx, group);
+ await this.addScrollJankV3ScrollTrack(ctx, group);
+ await ScrollJankCauseMap.initialize(ctx.engine);
+ ctx.workspace.addChildInOrder(group);
+ group.expand();
  }
 
  private async addTopLevelScrollTrack(