[DevTools] Fix null tooltip errors

third_party/WebKit/Source/devtools/front_end/ui/Tooltip.js

 // Copyright (c) 2015 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
  */
 UI.Tooltip = class {
   /**
    * @param {!Document} doc
    */
@@ skipping 11 matching lines @@
   }
 
   /**
    * @param {!Document} doc
    */
   static installHandler(doc) {
     new UI.Tooltip(doc);
   }
 
   /**
+   * Installs the tooltipContent to be shown on mouseover, called when title is set on an Element.

[lushnikov, 2016/12/06 01:19:37]

style: please, drop the documentation comment (i know, that sounds shocking, but
we don't use any)

[paulirish, 2016/12/06 01:37:27]

Isn't that old policy? Blink is open to comments for documentation now, aren't
we?

[lushnikov, 2016/12/06 22:30:23]

Let's discuss this on Thursday!

We should either write comments consistently or disregard them altogether.
I'd rather not, since front-end is not *that* big and moves quite fast.

[phulce, 2016/12/06 23:09:32]

Done.

+   * Removes the tooltip if content is null or empty.
+   *
    * @param {!Element} element
-   * @param {!Element|string} tooltipContent
+   * @param {?Element|string} tooltipContent
    * @param {string=} actionId
    * @param {!Object=} options
    */
   static install(element, tooltipContent, actionId, options) {
-    if (typeof tooltipContent === 'string' && tooltipContent === '') {
+    if (tooltipContent === null || tooltipContent === '') {

[lushnikov, 2016/12/06 01:19:36]

if (!tooltipContent) {
   ...
}

[phulce, 2016/12/06 23:09:32]

Done.

       delete element[UI.Tooltip._symbol];
       return;
     }
     element[UI.Tooltip._symbol] = {content: tooltipContent, actionId: actionId, options: options || {}};
   }
 
   /**
    * @param {!Element} element
    */
   static addNativeOverrideContainer(element) {
@@ skipping 142 matching lines @@
   },
 
   /**
    * @param {!Element|string} x
    * @this {!Element}
    */
   set: function(x) {
     UI.Tooltip.install(this, x);
   }
 });