--- a/browser/devtools/inspector/test/browser_inspector_bug_831693_combinator_suggestions.js
+++ b/browser/devtools/inspector/test/browser_inspector_bug_831693_combinator_suggestions.js
@@ -84,18 +84,17 @@ function test()
          JSON.stringify(suggestions));
     EventUtils.synthesizeKey(key, {}, inspector.panelWin);
   }
 
   function checkState(event) {
     inspector.searchSuggestions._lastQuery.then(() => {
       let [key, suggestions] = keyStates[state];
       let actualSuggestions = popup.getItems();
-      is(popup._panel.state == "open" || popup._panel.state == "showing"
-         ? actualSuggestions.length: 0, suggestions.length,
+      is(popup.isOpen ? actualSuggestions.length: 0, suggestions.length,
          "There are expected number of suggestions at " + state + "th step.");
       actualSuggestions = actualSuggestions.reverse();
       for (let i = 0; i < suggestions.length; i++) {
         is(suggestions[i][0], actualSuggestions[i].label,
            "The suggestion at " + i + "th index for " + state +
            "th step is correct.")
         is(suggestions[i][1] || 1, actualSuggestions[i].count,
            "The count for suggestion at " + i + "th index for " + state +

--- a/browser/devtools/inspector/test/browser_inspector_bug_831693_input_suggestion.js
+++ b/browser/devtools/inspector/test/browser_inspector_bug_831693_input_suggestion.js
@@ -85,18 +85,17 @@ function test()
          JSON.stringify(suggestions));
     EventUtils.synthesizeKey(key, {}, inspector.panelWin);
   }
 
   function checkState(event) {
     inspector.searchSuggestions._lastQuery.then(() => {
       let [key, suggestions] = keyStates[state];
       let actualSuggestions = popup.getItems();
-      is(popup._panel.state == "open" || popup._panel.state == "showing"
-         ? actualSuggestions.length: 0, suggestions.length,
+      is(popup.isOpen ? actualSuggestions.length: 0, suggestions.length,
          "There are expected number of suggestions at " + state + "th step.");
       actualSuggestions = actualSuggestions.reverse();
       for (let i = 0; i < suggestions.length; i++) {
         is(suggestions[i][0], actualSuggestions[i].label,
            "The suggestion at " + i + "th index for " + state +
            "th step is correct.")
         is(suggestions[i][1] || 1, actualSuggestions[i].count,
            "The count for suggestion at " + i + "th index for " + state +

--- a/browser/devtools/markupview/test/browser_bug896181_css_mixed_completion_new_attribute.js
+++ b/browser/devtools/markupview/test/browser_bug896181_css_mixed_completion_new_attribute.js
@@ -125,19 +125,17 @@ function test() {
       if (selEnd != -1) {
         is(editor.input.value, completion,
            "Correct value is autocompleted for state " + state);
         is(editor.input.selectionStart, selStart,
            "Selection is starting at the right location for state " + state);
         is(editor.input.selectionEnd, selEnd,
            "Selection is ending at the right location for state " + state);
         if (popupOpen) {
-          ok(editor.popup._panel.state == "open" ||
-             editor.popup._panel.state == "showing",
-             "Popup is open for state " + state);
+          ok(editor.popup.isOpen, "Popup is open for state " + state);
         }
         else {
           ok(editor.popup._panel.state != "open" &&
              editor.popup._panel.state != "showing",
              "Popup is closed for state " + state);
         }
       }
       else {

--- a/browser/devtools/shared/autocomplete-popup.js
+++ b/browser/devtools/shared/autocomplete-popup.js
@@ -154,17 +154,17 @@ AutocompletePopup.prototype = {
   {
     this._panel.hidePopup();
   },
 
   /**
    * Check if the autocomplete popup is open.
    */
   get isOpen() {
-    return this._panel.state == "open";
+    return this._panel.state == "open" || this._panel.state == "showing";
   },
 
   /**
    * Destroy the object instance. Please note that the panel DOM elements remain
    * in the DOM, because they might still be in use by other instances of the
    * same code. It is the responsability of the client code to perform DOM
    * cleanup.
    */

--- a/browser/devtools/sourceeditor/autocomplete.js
+++ b/browser/devtools/sourceeditor/autocomplete.js
@@ -25,25 +25,25 @@ function setupAutoCompletion(ctx, walker
     position: "after_start",
     fixedWidth: true,
     theme: "auto",
     autoSelect: true
   });
 
   let keyMap = {
     "Tab": cm => {
-      if (popup && (popup.isOpen || popup._panel.state == "showing")) {
+      if (popup && popup.isOpen) {
         cycleSuggestions(ed);
         return;
       }
 
       return win.CodeMirror.Pass;
     },
     "Shift-Tab": cm => {
-      if (popup && (popup.isOpen || popup._panel.state == "showing")) {
+      if (popup && popup.isOpen) {
         cycleSuggestions(ed, true);
         return;
       }
 
       return win.CodeMirror.Pass;
     },
   };
   keyMap[Editor.accel("Space")] = cm => autoComplete(ctx);

--- a/browser/devtools/styleeditor/test/browser_styleeditor_autocomplete.js
+++ b/browser/devtools/styleeditor/test/browser_styleeditor_autocomplete.js
@@ -120,18 +120,17 @@ function testState() {
   EventUtils.synthesizeKey(key, mods, gPanelWindow);
 }
 
 function checkState() {
   executeSoon(() => {
     info("After keypress for index " + index);
     let [key, total, current, inserted] = TEST_CASES[index];
     if (total != -1) {
-      ok(gPopup._panel.state == "open" || gPopup._panel.state == "showing",
-         "Popup is open for index " + index);
+      ok(gPopup.isOpen, "Popup is open for index " + index);
       is(total, gPopup.itemCount,
          "Correct total suggestions for index " + index);
       is(current, gPopup.selectedIndex,
          "Correct index is selected for index " + index);
       if (inserted) {
         let { preLabel, label } = gPopup.getItemAtIndex(current);
         let { line, ch } = gEditor.getCursor();
         let lineText = gEditor.getText(line);

--- a/browser/devtools/styleinspector/test/browser_bug893965_css_property_completion_new_property.js
+++ b/browser/devtools/styleinspector/test/browser_bug893965_css_property_completion_new_property.js
@@ -100,19 +100,17 @@ function checkState(event) {
       is(editor.input.value, completion,
          "Correct value is autocompleted for state " + state);
     }
     if (total == 0) {
       ok(!(editor.popup && editor.popup.isOpen), "Popup is closed for state " +
          state);
     }
     else {
-      ok(editor.popup._panel.state == "open" ||
-         editor.popup._panel.state == "showing",
-         "Popup is open for state " + state);
+      ok(editor.popup.isOpen, "Popup is open for state " + state);
       is(editor.popup.getItems().length, total,
          "Number of suggestions match for state " + state);
       is(editor.popup.selectedIndex, index,
          "Correct item is selected for state " + state);
     }
     checkStateAndMoveOn(state + 1);
   });
 }

--- a/browser/devtools/styleinspector/test/browser_bug894376_css_value_completion_existing_property_value_pair.js
+++ b/browser/devtools/styleinspector/test/browser_bug894376_css_value_completion_existing_property_value_pair.js
@@ -112,19 +112,17 @@ function checkState(event) {
       is(editor.input.value, completion,
          "Correct value is autocompleted for state " + state);
     }
     if (total == 0) {
       ok(!(editor.popup && editor.popup.isOpen), "Popup is closed for state " +
          state);
     }
     else {
-      ok(editor.popup._panel.state == "open" ||
-         editor.popup._panel.state == "showing",
-         "Popup is open for state " + state);
+      ok(editor.popup.isOpen, "Popup is open for state " + state);
       is(editor.popup.getItems().length, total,
          "Number of suggestions match for state " + state);
       is(editor.popup.selectedIndex, index,
          "Correct item is selected for state " + state);
     }
     checkStateAndMoveOn(state + 1);
   });
 }

--- a/browser/devtools/styleinspector/test/browser_bug894376_css_value_completion_new_property_value_pair.js
+++ b/browser/devtools/styleinspector/test/browser_bug894376_css_value_completion_new_property_value_pair.js
@@ -109,19 +109,17 @@ function checkState(event) {
       is(editor.input.value, completion,
          "Correct value is autocompleted for state " + state);
     }
     if (total == 0) {
       ok(!(editor.popup && editor.popup.isOpen), "Popup is closed for state " +
          state);
     }
     else {
-      ok(editor.popup._panel.state == "open" ||
-         editor.popup._panel.state == "showing",
-         "Popup is open for state " + state);
+      ok(editor.popup.isOpen, "Popup is open for state " + state);
       is(editor.popup.getItems().length, total,
          "Number of suggestions match for state " + state);
       is(editor.popup.selectedIndex, index,
          "Correct item is selected for state " + state);
     }
     checkStateAndMoveOn(state + 1);
   });
 }