DevTools: Show screenshots on the main flamechart

third_party/WebKit/Source/devtools/front_end/timeline/PerformanceModel.js

 // Copyright 2017 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.
 
 Timeline.PerformanceModel = class extends Common.Object {
   constructor() {
     super();
     /** @type {?SDK.Target} */
     this._mainTarget = null;
     /** @type {?SDK.TracingModel} */
@@ skipping 115 matching lines @@
   extensionInfo() {
     return this._extensionTracingModels;
   }
 
   dispose() {
     if (this._tracingModel)
       this._tracingModel.reset();
     for (var extensionEntry of this._extensionTracingModels)
       extensionEntry.model.reset();
   }
+
+  /**
+   * @param {!TimelineModel.TimelineFrame} frame
+   * @return {?SDK.FilmStripModel.Frame}
+   */
+  filmStripModelFrame(frame) {
+    // For idle frames, look at the state at the beginning of the frame.
+    var screenshotTime = frame.idle ? frame.startTime : frame.endTime;
+    var filmStripFrame = this._filmStripModel.frameByTimestamp(screenshotTime);
+    return filmStripFrame && filmStripFrame.timestamp - frame.endTime < 10 ? filmStripFrame : null;
+  }
 };
 
 /**
  * @enum {symbol}
  */
 Timeline.PerformanceModel.Events = {
   ExtensionDataAdded: Symbol('ExtensionDataAdded')
 };