DevTools: Fix flamechart jumping on mouseout

third_party/WebKit/Source/devtools/front_end/perf_ui/ChartViewport.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.
 
 /**
  * @unrestricted
  */
 PerfUI.ChartViewport = class extends UI.VBox {
   constructor() {
     super(true);
@@ skipping 154 matching lines @@
    * @param {!MouseEvent} event
    * @return {boolean}
    */
   _startDragging(event) {
     if (event.shiftKey)
       return false;
     if (this._windowRight === Infinity)
       return false;
     this._isDragging = true;
     this._initMaxDragOffset(event);
-    this._dragStartPointX = event.offsetX;
-    this._dragStartPointY = event.offsetY;
+    this._dragStartPointX = event.pageX;
+    this._dragStartPointY = event.pageY;
     this._dragStartScrollTop = this._vScrollElement.scrollTop;
     this.viewportElement.style.cursor = '';
     this.hideHighlight();
     return true;
   }
 
   /**
    * @param {!MouseEvent} event
    */
   _dragging(event) {
-    var pixelShift = this._dragStartPointX - event.offsetX;
-    this._dragStartPointX = event.offsetX;
+    var pixelShift = this._dragStartPointX - event.pageX;
+    this._dragStartPointX = event.pageX;
     this._muteAnimation = true;
     this._handlePanGesture(pixelShift * this._pixelToTime);
     this._muteAnimation = false;
-    var pixelScroll = this._dragStartPointY - event.offsetY;
+    var pixelScroll = this._dragStartPointY - event.pageY;
     this._vScrollElement.scrollTop = this._dragStartScrollTop + pixelScroll;
-    this._updateMaxDragOffset(event.offsetX, event.offsetY);
+    this._updateMaxDragOffset(event.pageX, event.pageY);
   }
 
   /**
    * @private
    */
   _endDragging() {
     this._isDragging = false;
     this._updateHighlight();
   }
 
@@ skipping 262 matching lines @@
     }
     this._cancelAnimation();
     this._cancelWindowTimesAnimation = UI.animateFunction(
         this.element.window(), this._animateWindowTimes.bind(this),
         [{from: this._timeWindowLeft, to: startTime}, {from: this._timeWindowRight, to: endTime}], 5,
         this._animationCompleted.bind(this));
     this._pendingAnimationTimeLeft = startTime;
     this._pendingAnimationTimeRight = endTime;
   }
 };