DevTools: move flow events tracking to TracingModel, support cross-threads case

third_party/WebKit/Source/devtools/front_end/sdk/TracingModel.js

Index: third_party/WebKit/Source/devtools/front_end/sdk/TracingModel.js
diff --git a/third_party/WebKit/Source/devtools/front_end/sdk/TracingModel.js b/third_party/WebKit/Source/devtools/front_end/sdk/TracingModel.js
index 996fc50311f94ae9feac104e0ecd159c9af2f65d..19949d4fd7355281dea85871a7403544f2384afb 100644
--- a/third_party/WebKit/Source/devtools/front_end/sdk/TracingModel.js
+++ b/third_party/WebKit/Source/devtools/front_end/sdk/TracingModel.js
@@ -118,6 +118,13 @@ SDK.TracingModel = class {
   }
 
   /**
+   * @return {!Array.<!SDK.TracingModel.Event>}
+   */
+  flowHeads() {
+    return this._flowHeads;
+  }
+
+  /**
    * @param {!Array.<!SDK.TracingManager.EventPayload>} events
    */
   setEventsForTest(events) {
@@ -136,6 +143,7 @@ SDK.TracingModel = class {
 
   tracingComplete() {
     this._processPendingAsyncEvents();
+    this._processFlowEvents();
     this._backingStorage.appendString(this._firstWritePending ? '[]' : ']');
     this._backingStorage.finishWriting();
     this._firstWritePending = false;
@@ -162,10 +170,14 @@ SDK.TracingModel = class {
     this._openAsyncEvents = new Map();
     /** @type {!Map<string, !Array<!SDK.TracingModel.AsyncEvent>>} */
     this._openNestableAsyncEvents = new Map();
+    /** @type {!Map<string, !Array<!SDK.TracingModel.Event>>} */
+    this._flowEventsById = new Map();
     /** @type {!Map<string, !SDK.TracingModel.ProfileEventsGroup>} */
     this._profileGroups = new Map();
     /** @type {!Map<string, !Set<string>>} */
     this._parsedCategories = new Map();
+    /** @type {!Array<!SDK.TracingModel.Event>} */
+    this._flowHeads = [];
   }
 
   /**
@@ -231,8 +243,18 @@ SDK.TracingModel = class {
     // Build async event when we've got events from all threads & processes, so we can sort them and process in the
     // chronological order. However, also add individual async events to the thread flow (above), so we can easily
     // display them on the same chart as other events, should we choose so.
-    if (SDK.TracingModel.isAsyncPhase(payload.ph))
+    if (SDK.TracingModel.isAsyncPhase(payload.ph)) {
       this._asyncEvents.push(event);
+    } else if (SDK.TracingModel.isFlowPhase(payload.ph)) {
+      var key = `${event.categoriesString}-${event.name}-${event.id}`;

[pfeldman, 2017/03/16 07:03:50]

I don't think categoriesString and event name should be a part of the key.

Overall, I'm looking at this +172 lines, -55 lines patch and I wonder why we are
adding all this complexity. The code was very readable before the change and now
it somewhat cryptic. I don't think we need this sorting, complex keys and model
api for our scenarios. I want to implement the tree shaking and I don't think
I'm going to use this API. At the same time, rendering code is now more complex.
All it all it seems complexity for the sake of complexity, so I wonder, why?

+      var flowEvents = this._flowEventsById.get(key);
+      if (!flowEvents) {
+        flowEvents = [];
+        this._flowEventsById.set(key, flowEvents);
+      }
+      flowEvents.push(event);
+    }
+
     event._setBackingStorage(backingStorage);
     if (event.hasCategory(SDK.TracingModel.DevToolsMetadataEventCategory))
       this._devToolsMetadataEvents.push(event);
@@ -329,6 +351,22 @@ SDK.TracingModel = class {
     this._closeOpenAsyncEvents();
   }
 
+  _processFlowEvents() {
+    var phases = SDK.TracingModel.Phase;
+    for (var events of this._flowEventsById.values()) {
+      events.stableSort(SDK.TracingModel.Event.compareStartTime);
+      var lastInChain = null;
+      for (var e of events) {
+        if (lastInChain && e.phase !== phases.FlowBegin)
+          lastInChain._appendFlowEvent(e);
+        if (!lastInChain && e.phase !== phases.FlowEnd)
+          this._flowHeads.push(e);

[pfeldman, 2017/03/16 02:00:22]

So if there is no begin, you still consider it a head?

+        lastInChain = e.phase !== phases.FlowEnd ? e : null;

[pfeldman, 2017/03/16 02:00:22]

why do you need all this logic? it is either begin-step-step-step-end or there
is a bug. if there is a bug, but consider the first one begin and the last one
an end.

+      }
+    }
+    this._flowEventsById.clear();
+  }
+
   _closeOpenAsyncEvents() {
     for (var event of this._openAsyncEvents.values()) {
       event.setEndTime(this._maximumRecordTime);
@@ -525,6 +563,10 @@ SDK.TracingModel.Event = class {
     this.thread = thread;
     /** @type {!Object} */
     this.args = {};
+    /** @type {!SDK.TracingModel.Event|undefined} */
+    this.nextFlow;
+    /** @type {!SDK.TracingModel.Event|undefined} */
+    this.previousFlow;
 
     /** @type {number} */
     this.selfTime = 0;
@@ -628,6 +670,14 @@ SDK.TracingModel.Event = class {
   }
 
   /**
+   * @param {!SDK.TracingModel.Event} nextFlow
+   */
+  _appendFlowEvent(nextFlow) {
+    this.nextFlow = nextFlow;
+    nextFlow.previousFlow = this;
+  }
+
+  /**
    * @param {?function():!Promise.<?string>} backingStorage
    */
   _setBackingStorage(backingStorage) {