DevTools: add entry points for command menu

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

 /*
  * Copyright (C) 2010 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 471 matching lines @@
     else
       constraints = constraints.addHeight(new UI.Constraints(new UI.Size(0, 30)));
     return constraints;
   }
 
   _updateTabElements() {
     UI.invokeOnceAfterBatchUpdate(this, this._innerUpdateTabElements);
   }
 
   /**
-   * @param {string} text
+   * @param {!Element} element
    */
-  setPlaceholderText(text) {
-    this._noTabsMessage = text;
+  setPlaceholderElement(element) {

[pfeldman, 2017/04/26 00:02:21]

This call seems to have no effect on its own.

[luoe, 2017/04/26 01:40:56]

Semantically, calling setPlaceholderElement() after an old placeholderElement
has been rendered should update the container with the new one.

+    this._placeholderElement = element;
   }
 
   _innerUpdateTabElements() {
     if (!this.isShowing())
       return;
 
     if (!this._tabs.length) {
       this._contentElement.classList.add('has-no-tabs');
-      if (this._noTabsMessage && !this._noTabsMessageElement) {
-        this._noTabsMessageElement = this._contentElement.createChild('div', 'tabbed-pane-placeholder fill');
-        this._noTabsMessageElement.textContent = this._noTabsMessage;
+      if (this._placeholderElement && !this._placeholderContainerElement) {
+        this._placeholderContainerElement = this._contentElement.createChild('div', 'tabbed-pane-placeholder fill');
+        this._placeholderContainerElement.appendChild(this._placeholderElement);
       }
     } else {
       this._contentElement.classList.remove('has-no-tabs');
-      if (this._noTabsMessageElement) {
-        this._noTabsMessageElement.remove();
-        delete this._noTabsMessageElement;
+      if (this._placeholderContainerElement) {
+        this._placeholderContainerElement.remove();
+        delete this._placeholderContainerElement;
       }
     }
 
     this._measureDropDownButton();
     this._updateWidths();
     this._updateTabsDropDown();
     this._updateTabSlider();
   }
 
   /**
@@ skipping 697 matching lines @@
    * @param {!Array.<string>} ids
    */
   closeTabs(tabbedPane, ids) {},
 
   /**
    * @param {string} tabId
    * @param {!UI.ContextMenu} contextMenu
    */
   onContextMenu(tabId, contextMenu) {}
 };