DevTools: [Timeline] Reset Memory Overview pane when clear button is clicked

Source/devtools/front_end/TimelineOverviewPane.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 445 matching lines @@
     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 = {
     update: function()
     {
+        this._resetCanvas();
+
         var records = this._model.records;
         if (!records.length)
             return;
 
-        this._resetCanvas();
-
         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) {
             maxUsedHeapSize = Math.max(maxUsedHeapSize, r.usedHeapSize || maxUsedHeapSize);
             minUsedHeapSize = Math.min(minUsedHeapSize, r.usedHeapSize || minUsedHeapSize);
         });
         minUsedHeapSize = Math.min(minUsedHeapSize, maxUsedHeapSize);
 
         var width = this._canvas.width;
         var height = this._canvas.height - lowerOffset;
         var xFactor = width / (maxTime - minTime);
         var yFactor = height / Math.max(maxUsedHeapSize - minUsedHeapSize, 1);
 
         var histogram = new Array(width);
         WebInspector.TimelinePresentationModel.forAllRecords(records, function(r) {
             if (!r.usedHeapSize)
                 return;
             var x = Math.round((WebInspector.TimelineModel.endTimeInSeconds(r) - minTime) * xFactor);
             var y = Math.round((r.usedHeapSize - minUsedHeapSize) * yFactor);
             histogram[x] = Math.max(histogram[x] || 0, y);
         });
 
-        var ctx = this._context;
-        this._clear(ctx);
-
         height++; // +1 so that the border always fit into the canvas area.
 
         var y = 0;
         var isFirstPoint = true;
+        var ctx = this._context;
         ctx.beginPath();
         ctx.moveTo(0, this._canvas.height);
         for (var x = 0; x < histogram.length; x++) {
             if (typeof histogram[x] === "undefined")
                 continue;
             if (isFirstPoint) {
                 isFirstPoint = false;
                 y = histogram[x];
                 ctx.lineTo(0, height - y);
             }
@@ skipping 10 matching lines @@
         ctx.strokeStyle = "rgba(20,0,0,0.8)";
         ctx.stroke();
 
         ctx.fillStyle = "rgba(214,225,254, 0.8);";
         ctx.fill();
 
         this._maxHeapSizeLabel.textContent = Number.bytesToString(maxUsedHeapSize);
         this._minHeapSizeLabel.textContent = Number.bytesToString(minUsedHeapSize);
     },
 
-    _clear: function(ctx)
-    {
-        ctx.fillStyle = "rgba(255,255,255,0.8)";
-        ctx.fillRect(0, 0, this._canvas.width, this._canvas.height);
-    },
-
     __proto__: WebInspector.TimelineOverviewBase.prototype
 }
 
 /**
  * @constructor
  * @extends {WebInspector.TimelineOverviewBase}
  * @param {WebInspector.TimelineModel} model
  */
 WebInspector.TimelineEventOverview = function(model)
 {
@@ skipping 413 matching lines @@
 WebInspector.TimelineWindowFilter.prototype = {
     /**
      * @param {!WebInspector.TimelinePresentationModel.Record} record
      * @return {boolean}
      */
     accept: function(record)
     {
         return record.lastChildEndTime >= this._pane._windowStartTime && record.startTime <= this._pane._windowEndTime;
     }
 }