[DevTools] Turn starting tracing into promise.

third_party/WebKit/Source/devtools/front_end/network/NetworkPanel.js

Index: third_party/WebKit/Source/devtools/front_end/network/NetworkPanel.js
diff --git a/third_party/WebKit/Source/devtools/front_end/network/NetworkPanel.js b/third_party/WebKit/Source/devtools/front_end/network/NetworkPanel.js
index f09dbedf04845abf4722852af58274fb81862b44..d641105249321b945c5501a14a17bd3e548957b3 100644
--- a/third_party/WebKit/Source/devtools/front_end/network/NetworkPanel.js
+++ b/third_party/WebKit/Source/devtools/front_end/network/NetworkPanel.js
@@ -699,10 +699,12 @@ Network.NetworkPanel.FilmStripRecorder = class {
     if (!this._tracingModel || !this._target)
       return;
     this._tracingModel.tracingComplete();
-    SDK.targetManager.resumeReload(this._target);
+    var resourceTreeModel = SDK.ResourceTreeModel.fromTarget(this._target);

[caseq, 2017/02/27 23:13:38]

nit: move down to actual usage.

[dgozman, 2017/02/28 01:58:17]

this._target is reset in next line.

     this._target = null;
     this._callback(new SDK.FilmStripModel(this._tracingModel, this._timeCalculator.minimumBoundary() * 1000));
     delete this._callback;
+    if (resourceTreeModel)
+      resourceTreeModel.resumeReload();
   }
 
   /**
@@ -747,7 +749,9 @@ Network.NetworkPanel.FilmStripRecorder = class {
       return;
 
     this._target.tracingManager.stop();
-    SDK.targetManager.suspendReload(this._target);
+    var resourceTreeModel = SDK.ResourceTreeModel.fromTarget(this._target);
+    if (resourceTreeModel)
+      resourceTreeModel.suspendReload();
     this._callback = callback;
     this._filmStripView.setStatusText(Common.UIString('Fetching frames...'));
   }