DevTools: Stop SuggestBox from flickering in TextPrompt

BUG=none

Review-Url: https://codereview.chromium.org/2390933003
Cr-Commit-Position: refs/heads/master@{#423016}

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

@@ -282,7 +282,7 @@ WebInspector.TextPrompt.prototype = {
      */
     _updateAutoComplete: function(force)
     {
-        this.clearAutocomplete();
+        this._clearAutocompleteElement();
         this.autoCompleteSoon(force);
     },
 
@@ -376,7 +376,11 @@ WebInspector.TextPrompt.prototype = {
     {
         if (this.isSuggestBoxVisible())
             this._suggestBox.hide();
+        this._clearAutocompleteElement();
+    },
 
+    _clearAutocompleteElement: function()
+    {
         if (this._completeTimeout) {
             clearTimeout(this._completeTimeout);
             delete this._completeTimeout;