Timeline: fix screenshots for headless shell

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

 /*
  * Copyright 2014 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.BackingStorage} backingStorage
  */
@@ skipping 99 matching lines @@
     var scope = payload.scope || "";
     if (typeof payload.id2 === "undefined")
         return scope && payload.id ? `${scope}@${payload.id}` : payload.id;
     var id2 = payload.id2;
     if (typeof id2 === "object" && ("global" in id2) !== ("local" in id2))
         return typeof id2["global"] !== "undefined" ? `:${scope}:${id2["global"]}` : `:${scope}:${payload.pid}:${id2["local"]}`;
     console.error(`Unexpected id2 field at ${payload.ts / 1000}, one and only one of 'local' and 'global' should be present.`);
 }
 
 /**
+ * @param {!WebInspector.TracingModel} tracingModel
+ * @return {?WebInspector.TracingModel.Thread}
+ *
+ * TODO: Move this to a better place. This is here just for convenience o
+ * re-use between modules. This really belongs to a higher level, since it
+ * is specific to chrome's usage of tracing.
+ */
+WebInspector.TracingModel.browserMainThread = function(tracingModel)
+{
+    var processes = tracingModel.sortedProcesses();
+    var browserProcesses = [];
+    var crRendererMainThreads = [];
+    for (var process of processes) {
+        if (process.name().toLowerCase().endsWith("browser"))
+            browserProcesses.push(process);
+        crRendererMainThreads.push(...process.sortedThreads().filter(t => t.name() === "CrBrowserMain"));
+    }
+    if (crRendererMainThreads.length === 1)
+        return crRendererMainThreads[0];
+    if (browserProcesses.length === 1)
+        return browserProcesses[0].threadByName("CrBrowserMain");
+    var tracingStartedInBrowser = tracingModel.devToolsMetadataEvents().filter(e => e.name === "TracingStartedInBrowser");
+    if (tracingStartedInBrowser.length === 1)
+        return tracingStartedInBrowser[0].thread;
+    WebInspector.console.error("Failed to find browser main thread in trace, some timeline features may be unavailable");
+    return null;
+}
+
+/**
  * @interface
  */
 WebInspector.BackingStorage = function()
 {
 }
 
 WebInspector.BackingStorage.prototype = {
     /**
      * @param {string} string
      */
@@ skipping 817 matching lines @@
     /**
      * @return {!Array.<!WebInspector.TracingModel.AsyncEvent>}
      */
     asyncEvents: function()
     {
         return this._asyncEvents;
     },
 
     __proto__: WebInspector.TracingModel.NamedObject.prototype
 }