Devtools UI: Remove redundant tooltips

Source/devtools/front_end/ui/treeoutline.js

 /*
  * Copyright (C) 2007 Apple 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 294 matching lines @@
     /** @type {?TreeOutline} */
     this.treeOutline = null;
     this.parent = null;
     this.previousSibling = null;
     this.nextSibling = null;
 
     this._listItemNode = createElement("li");
     this._listItemNode.treeElement = this;
     if (title)
         this.title = title;
-    if (typeof title === "string")
-        this.tooltip = title;

[paulirish, 2015/08/03 16:26:20]

Appears to be useful for truncated strings like data uris

http://i.imgur.com/aOd4vGd.png

I'd be fine with removing if we knew the displayed text was identical, but
otherwise it seems useful to keep for these cases

[samli, 2015/08/05 07:53:31]

This is not that and still works. The only instances I could find where this was
used was where the string was either empty or:
CPU PROFILES
HEAP SNAPSHOTS
HEAP TIMELINES
RESULTS

This is actually where the empty tooltip bug is coming from.

     this._listItemNode.addEventListener("mousedown", this._handleMouseDown.bind(this), false);
     this._listItemNode.addEventListener("selectstart", this._treeElementSelectStart.bind(this), false);
     this._listItemNode.addEventListener("click", this._treeElementToggled.bind(this), false);
     this._listItemNode.addEventListener("dblclick", this._handleDoubleClick.bind(this), false);
 
     this._childrenListNode = createElement("ol");
     this._childrenListNode.parentTreeElement = this;
     this._childrenListNode.classList.add("children");
 
     this._hidden = false;
@@ skipping 725 matching lines @@
     isEventWithinDisclosureTriangle: function(event)
     {
         // FIXME: We should not use getComputedStyle(). For that we need to get rid of using ::before for disclosure triangle. (http://webk.it/74446)
         var paddingLeftValue = window.getComputedStyle(this._listItemNode).paddingLeft;
         console.assert(paddingLeftValue.endsWith("px"));
         var computedLeftPadding = parseFloat(paddingLeftValue);
         var left = this._listItemNode.totalOffsetLeft() + computedLeftPadding;
         return event.pageX >= left && event.pageX <= left + TreeElement._ArrowToggleWidth && this._expandable;
     }
 }