Timeline: fix NPE in heavy stack view when clearing Timeline

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

 // Copyright 2016 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.
 
 /**
  * @implements {Timeline.TimelineModeView}
  * @implements {PerfUI.FlameChartDelegate}
  * @implements {UI.Searchable}
  * @unrestricted
  */
@@ skipping 97 matching lines @@
    * @override
    * @param {?Timeline.PerformanceModel} model
    */
   setModel(model) {
     var extensionDataAdded = Timeline.PerformanceModel.Events.ExtensionDataAdded;
     if (this._model)
       this._model.removeEventListener(extensionDataAdded, this._appendExtensionData, this);
     this._model = model;
     if (this._model)
       this._model.addEventListener(extensionDataAdded, this._appendExtensionData, this);
+    this._mainDataProvider.setModel(this._model);
+    this._networkDataProvider.setModel(this._model);
+    this._countersView.setModel(this._model);
+    this._detailsView.setModel(this._model);
+
+    this._nextExtensionIndex = 0;
+    this._appendExtensionData();
+
     this._updateSearchHighlight(false, true);
     this._refresh();
   }
 
   _refresh() {
-    this._mainDataProvider.setModel(this._model);
-    this._networkDataProvider.setModel(this._model);
-    this._countersView.setModel(this._model);
-    if (this._detailsView)
-      this._detailsView.setModel(this._model);
-
-    this._nextExtensionIndex = 0;
-    this._appendExtensionData();
-
     if (this._networkDataProvider.isEmpty()) {
       this._mainFlameChart.enableRuler(true);
       this._networkSplitWidget.hideSidebar();
     } else {
       this._mainFlameChart.enableRuler(false);
       this._networkSplitWidget.showBoth();
       this.resizeToPreferredHeights();
     }
     this._mainFlameChart.reset();
     this._networkFlameChart.reset();
@@ skipping 359 matching lines @@
       context.translate(this._style.lineWidth < 1 || (this._style.lineWidth & 1) ? 0.5 : 0, 0.5);
       context.beginPath();
       context.moveTo(x, height);
       context.setLineDash(this._style.dashStyle);
       context.lineTo(x, context.canvas.height);
       context.stroke();
     }
     context.restore();
   }
 };