[RPP] Use FlowsHandler data in initiators handler

Use it to automatically compute initiator relationships of flow events
(in this case only SchedulePostMessage-HandlePostMessage pairs, since
that's the only trace event pair using the perfetto's flow API atm).

Bug: 381033695
Change-Id: Ic517df29c78c3f2537417d1653827d10d67fc107
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6048879
Reviewed-by: Jack Franklin <jacktfranklin@chromium.org>
Commit-Queue: Andres Olivares <andoli@chromium.org>

Author: and-oli

front_end/models/trace/handlers/InitiatorsHandler.test.ts

@@ -194,8 +194,10 @@ describe('InitiatorsHandler', () => {
   it('for a PostMessage Handler event the initiator is the PostMessage Dispatch event', async function() {
     const traceEvents = await TraceLoader.rawEvents(this, 'postmessage-initiators.json.gz');
     for (const event of traceEvents) {
+      Trace.Handlers.ModelHandlers.FlowsHandler.handleEvent(event);
       Trace.Handlers.ModelHandlers.Initiators.handleEvent(event);
     }
+    await Trace.Handlers.ModelHandlers.FlowsHandler.finalize();
     await Trace.Handlers.ModelHandlers.Initiators.finalize();
     const data = Trace.Handlers.ModelHandlers.Initiators.data();
 

front_end/models/trace/handlers/InitiatorsHandler.ts

@@ -5,6 +5,8 @@
 import * as Helpers from '../helpers/helpers.js';
 import * as Types from '../types/types.js';
 
+import {data as flowsHandlerData} from './FlowsHandler.js';
+
 const lastScheduleStyleRecalcByFrame = new Map<string, Types.Events.ScheduleStyleRecalculation>();
 
 // This tracks the last event that is considered to have invalidated the layout
@@ -20,10 +22,6 @@ const lastInvalidationEventForFrame = new Map<string, Types.Events.Event>();
 // is called.
 const lastUpdateLayoutTreeByFrame = new Map<string, Types.Events.UpdateLayoutTree>();
 
-// This tracks postmessage dispatch and handler events for creating initiator association
-const postMessageHandlerEvents: Types.Events.HandlePostMessage[] = [];
-const schedulePostMessageEventByTraceId: Map<string, Types.Events.SchedulePostMessage> = new Map();
-
 // These two maps store the same data but in different directions.
 // For a given event, tell me what its initiator was. An event can only have one initiator.
 const eventToInitiatorMap = new Map<Types.Events.Event, Types.Events.Event>();
@@ -48,8 +46,6 @@ export function reset(): void {
   requestIdleCallbackEventsById.clear();
   webSocketCreateEventsById.clear();
   schedulePostTaskCallbackEventsById.clear();
-  schedulePostMessageEventByTraceId.clear();
-  postMessageHandlerEvents.length = 0;
 }
 
 function storeInitiator(data: {initiator: Types.Events.Event, event: Types.Events.Event}): void {
@@ -164,34 +160,20 @@ export function handleEvent(event: Types.Events.Event): void {
       storeInitiator({event, initiator: matchingSchedule});
     }
   }
-  // Store schedulePostMessage Events by their traceIds.
-  // so they can be reconciled later with matching handlePostMessage events with same traceIds.
-  else if (Types.Events.isHandlePostMessage(event)) {
-    postMessageHandlerEvents.push(event);
-  } else if (Types.Events.isSchedulePostMessage(event)) {
-    const traceId = event.args.data?.traceId;
-    if (traceId) {
-      schedulePostMessageEventByTraceId.set(traceId, event);
-    }
-  }
 }
 
-function finalizeInitiatorRelationship(): void {
-  for (const handlerEvent of postMessageHandlerEvents) {
-    const traceId = handlerEvent.args.data?.traceId;
-    const matchingSchedulePostMesssageEvent = schedulePostMessageEventByTraceId.get(traceId);
-    if (matchingSchedulePostMesssageEvent) {
-      // Set schedulePostMesssage events as initiators for handler events.
-      storeInitiator({event: handlerEvent, initiator: matchingSchedulePostMesssageEvent});
+function createRelationshipsFromFlows(): void {
+  const flows = flowsHandlerData().flows;
+  for (let i = 0; i < flows.length; i++) {
+    const flow = flows[i];
+    for (let j = 0; j < flow.length - 1; j++) {
+      storeInitiator({event: flow[j + 1], initiator: flow[j]});
     }
   }
 }
 
 export async function finalize(): Promise<void> {
-  // During event processing, we may encounter initiators before the handler events themselves
-  // (e.g dispatch events on worker and handler events on the main thread)
-  // we don't want to miss out on events whose initiators haven't been processed yet
-  finalizeInitiatorRelationship();
+  createRelationshipsFromFlows();
 }
 
 export interface InitiatorsData {
@@ -205,3 +187,7 @@ export function data(): InitiatorsData {
     initiatorToEvents: initiatorToEventsMap,
   };
 }
+
+export function deps(): ['FlowsHandler'] {
+  return ['FlowsHandler'];
+}