Clear button doesn't clear everything in memory section.

Source/devtools/front_end/TimelineMemoryOverview.js

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 25 matching lines @@
 WebInspector.TimelineMemoryOverview = function(model)
 {
     WebInspector.TimelineOverviewBase.call(this, model);
     this.element.id = "timeline-overview-memory";
 
     this._maxHeapSizeLabel = this.element.createChild("div", "max memory-graph-label");
     this._minHeapSizeLabel = this.element.createChild("div", "min memory-graph-label");
 }
 
 WebInspector.TimelineMemoryOverview.prototype = {
+    resetHeapSizeLabels: function()
+    {
+        this._maxHeapSizeLabel.textContent = "";
+        this._minHeapSizeLabel.textContent = "";
+    },
+
     update: function()
     {
         this.resetCanvas();
 
         var records = this._model.records;
-        if (!records.length)
+        if (!records.length) {
+            this.resetHeapSizeLabels();
             return;
+        }
 
         const lowerOffset = 3;
         var maxUsedHeapSize = 0;
         var minUsedHeapSize = 100000000000;
         var minTime = this._model.minimumRecordTime();
         var maxTime = this._model.maximumRecordTime();
         WebInspector.TimelinePresentationModel.forAllRecords(records, function(r) {
             if (!r.counters || !r.counters.jsHeapSizeUsed)
                 return;
             maxUsedHeapSize = Math.max(maxUsedHeapSize, r.counters.jsHeapSizeUsed);
@@ skipping 49 matching lines @@
         ctx.strokeStyle = "#666";
         ctx.stroke();
         ctx.restore();
 
         this._maxHeapSizeLabel.textContent = Number.bytesToString(maxUsedHeapSize);
         this._minHeapSizeLabel.textContent = Number.bytesToString(minUsedHeapSize);
     },
 
     __proto__: WebInspector.TimelineOverviewBase.prototype
 }