DevTools: [Console] fix certain case that forces console to shake

Source/devtools/front_end/ui/ViewportControl.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 332 matching lines @@
             else if (this._headSelection.item > this._lastVisibleIndex)
                 headElement = this._bottomGapElement;
             headOffset = this._selectionIsBackward ? 0 : 1;
         }
 
         selection.setBaseAndExtent(anchorElement, anchorOffset, headElement, headOffset);
     },
 
     refresh: function()
     {
-        if (!this.element.clientHeight)
+        if (!this._visibleHeight())
             return;  // Do nothing for invisible controls.
 
         var itemCount = this._provider.itemCount();
         if (!itemCount) {
             for (var i = 0; i < this._renderedItems.length; ++i)
                 this._renderedItems[i].cacheFastHeight();
             for (var i = 0; i < this._renderedItems.length; ++i)
                 this._renderedItems[i].willHide();
             this._renderedItems = [];
             this._contentElement.removeChildren();
             this._topGapElement.style.height = "0px";
             this._bottomGapElement.style.height = "0px";
             this._firstVisibleIndex = -1;
             this._lastVisibleIndex = -1;
             return;
         }
 
         var selection = window.getSelection();
         var shouldRestoreSelection = this._updateSelectionModel(selection);
 
         var visibleFrom = this.element.scrollTop;
-        var clientHeight = this.element.clientHeight;
+        var visibleHeight = this._visibleHeight();
         var shouldStickToBottom = this._stickToBottom && this.element.isScrolledToBottom();
         var isInvalidating = !this._cumulativeHeights;
 
         if (this._cumulativeHeights && itemCount !== this._cumulativeHeights.length)
             delete this._cumulativeHeights;
         for (var i = 0; i < this._renderedItems.length; ++i) {
             this._renderedItems[i].cacheFastHeight();
             // Tolerate 1-pixel error due to double-to-integer rounding errors.
             if (this._cumulativeHeights && Math.abs(this._cachedItemHeight(this._firstVisibleIndex + i) - this._provider.fastHeight(i + this._firstVisibleIndex)) > 1)
                 delete this._cumulativeHeights;
         }
         this._rebuildCumulativeHeightsIfNeeded();
         var oldFirstVisibleIndex = this._firstVisibleIndex;
         var oldLastVisibleIndex = this._lastVisibleIndex;
         if (shouldStickToBottom) {
             this._lastVisibleIndex = itemCount - 1;
-            this._firstVisibleIndex = Math.max(itemCount - Math.ceil(clientHeight / this._provider.minimumRowHeight()), 0);
+            this._firstVisibleIndex = Math.max(itemCount - Math.ceil(visibleHeight / this._provider.minimumRowHeight()), 0);
         } else {
             this._firstVisibleIndex = Math.max(Array.prototype.lowerBound.call(this._cumulativeHeights, visibleFrom + 1), 0);
             // Proactively render more rows in case some of them will be collapsed without triggering refresh. @see crbug.com/390169
-            this._lastVisibleIndex = this._firstVisibleIndex + Math.ceil(clientHeight / this._provider.minimumRowHeight()) - 1;
+            this._lastVisibleIndex = this._firstVisibleIndex + Math.ceil(visibleHeight / this._provider.minimumRowHeight()) - 1;
             this._lastVisibleIndex = Math.min(this._lastVisibleIndex, itemCount - 1);
         }
         var topGapHeight = this._cumulativeHeights[this._firstVisibleIndex - 1] || 0;
         var bottomGapHeight = this._cumulativeHeights[this._cumulativeHeights.length - 1] - this._cumulativeHeights[this._lastVisibleIndex];
 
         this._topGapElement.style.height = topGapHeight + "px";
         this._bottomGapElement.style.height = bottomGapHeight + "px";
         this._topGapElement._active = !!topGapHeight;
         this._bottomGapElement._active = !!bottomGapHeight;
 
@@ skipping 172 matching lines @@
         this.element.scrollTop = index > 0 ? this._cumulativeHeights[index - 1] : 0;
         this.refresh();
     },
 
     /**
      * @param {number} index
      */
     forceScrollItemToBeLast: function(index)
     {
         this._rebuildCumulativeHeightsIfNeeded();
-        this.element.scrollTop = this._cumulativeHeights[index] - this.element.clientHeight;
+        this.element.scrollTop = this._cumulativeHeights[index] - this._visibleHeight();
         this.refresh();
+    },
+
+    /**
+     * @return {number}
+     */
+    _visibleHeight: function()
+    {
+        // Use offsetHeight instead of clientHeight to avoid being affected by horizontal scroll.
+        return this.element.offsetHeight;
     }
 }