[DevTools] Fix null tooltip errors

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

Index: third_party/WebKit/Source/devtools/front_end/ui/Tooltip.js
diff --git a/third_party/WebKit/Source/devtools/front_end/ui/Tooltip.js b/third_party/WebKit/Source/devtools/front_end/ui/Tooltip.js
index 4e41b8265d35cbd639ebad6cfb948363360ba6da..047eefef73d712fc8d93d6a3ec040f449708aeb7 100644
--- a/third_party/WebKit/Source/devtools/front_end/ui/Tooltip.js
+++ b/third_party/WebKit/Source/devtools/front_end/ui/Tooltip.js
@@ -30,12 +30,12 @@ UI.Tooltip = class {
 
   /**
    * @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) {
       delete element[UI.Tooltip._symbol];
       return;
     }