Timeline: always create filmstrip model and share single instance of it

third_party/WebKit/Source/devtools/front_end/components_lazy/FilmStripModel.js

 /*
  * Copyright 2015 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.
  */
 
 /**
  * @constructor
  * @param {!WebInspector.TracingModel} tracingModel
  * @param {number=} zeroTime
  */
 WebInspector.FilmStripModel = function(tracingModel, zeroTime)
 {
-    this._tracingModel = tracingModel;
-    this._zeroTime = zeroTime || tracingModel.minimumRecordTime();
-
-    /** @type {!Array<!WebInspector.FilmStripModel.Frame>} */
-    this._frames = [];
-
-    var browserProcess = tracingModel.processByName("Browser");
-    if (!browserProcess)
-        return;
-    var mainThread = browserProcess.threadByName("CrBrowserMain");
-    if (!mainThread)
-        return;
-
-    var events = mainThread.events();
-    for (var i = 0; i < events.length; ++i) {
-        var event = events[i];
-        if (event.startTime < this._zeroTime)
-            continue;
-        if (!event.hasCategory(WebInspector.FilmStripModel._category))
-            continue;
-        if (event.name === WebInspector.FilmStripModel.TraceEvents.CaptureFrame) {
-            var data = event.args["data"];
-            if (data)
-                this._frames.push(WebInspector.FilmStripModel.Frame._fromEvent(this, event, this._frames.length));
-        } else if (event.name === WebInspector.FilmStripModel.TraceEvents.Screenshot) {
-            this._frames.push(WebInspector.FilmStripModel.Frame._fromSnapshot(this, /** @type {!WebInspector.TracingModel.ObjectSnapshot} */ (event), this._frames.length));
-        }
-    }
+    this.reset(tracingModel, zeroTime);
 }
 
 WebInspector.FilmStripModel._category = "disabled-by-default-devtools.screenshot";
 
 WebInspector.FilmStripModel.TraceEvents = {
     CaptureFrame: "CaptureFrame",
     Screenshot: "Screenshot"
 }
 
 WebInspector.FilmStripModel.prototype = {
     /**
+     * @param {!WebInspector.TracingModel} tracingModel
+     * @param {number=} zeroTime
+     */
+    reset: function(tracingModel, zeroTime)

[alph, 2016/09/08 00:03:07]

you don't need to pass tracingModel all the time. It doesn't change.
Also is zeroTime ever passed here?

+    {
+        this._zeroTime = zeroTime || tracingModel.minimumRecordTime();
+        this._spanTime = tracingModel.maximumRecordTime() - this._zeroTime;
+
+        /** @type {!Array<!WebInspector.FilmStripModel.Frame>} */
+        this._frames = [];
+
+        var browserProcess = tracingModel.processByName("Browser");
+        if (!browserProcess)
+            return;
+        var mainThread = browserProcess.threadByName("CrBrowserMain");
+        if (!mainThread)
+            return;
+
+        var events = mainThread.events();
+        for (var i = 0; i < events.length; ++i) {
+            var event = events[i];
+            if (event.startTime < this._zeroTime)
+                continue;
+            if (!event.hasCategory(WebInspector.FilmStripModel._category))
+                continue;
+            if (event.name === WebInspector.FilmStripModel.TraceEvents.CaptureFrame) {
+                var data = event.args["data"];
+                if (data)
+                    this._frames.push(WebInspector.FilmStripModel.Frame._fromEvent(this, event, this._frames.length));
+            } else if (event.name === WebInspector.FilmStripModel.TraceEvents.Screenshot) {
+                this._frames.push(WebInspector.FilmStripModel.Frame._fromSnapshot(this, /** @type {!WebInspector.TracingModel.ObjectSnapshot} */ (event), this._frames.length));
+            }
+        }
+    },
+
+    /**
      * @return {!Array<!WebInspector.FilmStripModel.Frame>}
      */
     frames: function()
     {
         return this._frames;
     },
 
     /**
      * @return {number}
      */
     zeroTime: function()
     {
         return this._zeroTime;
     },
 
     /**
+     * @return {number}
+     */
+    spanTime: function()
+    {
+        return this._spanTime;
+    },
+
+    /**
      * @param {number} timestamp
      * @return {?WebInspector.FilmStripModel.Frame}
      */
     frameByTimestamp: function(timestamp)
     {
         var index = this._frames.upperBound(timestamp, (timestamp, frame) => timestamp - frame.timestamp) - 1;
         return index >= 0 ? this._frames[index] : null;
     }
 }
 
@@ skipping 53 matching lines @@
      * @return {!Promise<?string>}
      */
     imageDataPromise: function()
     {
         if (this._imageData || !this._snapshot)
             return Promise.resolve(this._imageData);
 
         return /** @type {!Promise<?string>} */ (this._snapshot.objectPromise());
     }
 }