DevTools: always zoom on wheel in flame chart.

Source/devtools/front_end/components/FlameChart.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 545 matching lines @@
         if (this._highlightedEntryIndex === -1)
             return;
         this.dispatchEventToListeners(WebInspector.FlameChart.Events.EntrySelected, this._highlightedEntryIndex);
     },
 
     /**
      * @param {!Event} e
      */
     _onMouseWheel: function(e)
     {
-        var scrollIsThere = this._totalHeight > this._offsetHeight;
-
+        // Pan vertically when shift down only.
+        var panVertically = e.shiftKey && (e.wheelDeltaY || Math.abs(e.wheelDeltaX) === 120);
         var panHorizontally = Math.abs(e.wheelDeltaX) > Math.abs(e.wheelDeltaY) && !e.shiftKey;
-        var panVertically = scrollIsThere && ((e.wheelDeltaY && !e.shiftKey) || (Math.abs(e.wheelDeltaX) === 120 && !e.shiftKey));
         if (panVertically) {
-            this._vScrollElement.scrollTop -= e.wheelDeltaY / 120 * this._offsetHeight / 8;
+            this._vScrollElement.scrollTop -= (e.wheelDeltaY || e.wheelDeltaX) / 120 * this._offsetHeight / 8;
         } else if (panHorizontally) {
             var shift = -e.wheelDeltaX * this._pixelToTime;
             this._muteAnimation = true;
             this._handlePanGesture(shift);
             this._muteAnimation = false;
         } else {  // Zoom.
             const mouseWheelZoomSpeed = 1 / 120;
             this._handleZoomGesture(Math.pow(1.2, -(e.wheelDeltaY || e.wheelDeltaX) * mouseWheelZoomSpeed) - 1);
         }
 
@@ skipping 592 matching lines @@
     {
         this._highlightedMarkerIndex = -1;
         this._highlightedEntryIndex = -1;
         this._selectedEntryIndex = -1;
         this._textWidth = {};
         this.update();
     },
 
     __proto__: WebInspector.HBox.prototype
 }