Revert "Remove the Social API"

browser/components/customizableui/CustomizableWidgets.jsm

@@ -556,6 +556,47 @@ const CustomizableWidgets = [
       clearSubview(sidebarItems);
       fillSubviewFromMenuItems([...menu.children], sidebarItems);
     }
+  }, {
+    id: "social-share-button",
+    // custom build our button so we can attach to the share command
+    type: "custom",
+    onBuild: function(aDocument) {
+      let node = aDocument.createElementNS(kNSXUL, "toolbarbutton");
+      node.setAttribute("id", this.id);
+      node.classList.add("toolbarbutton-1");
+      node.classList.add("chromeclass-toolbar-additional");
+      node.setAttribute("label", CustomizableUI.getLocalizedProperty(this, "label"));
+      node.setAttribute("tooltiptext", CustomizableUI.getLocalizedProperty(this, "tooltiptext"));
+      node.setAttribute("removable", "true");
+      node.setAttribute("observes", "Social:PageShareable");
+      node.setAttribute("command", "Social:SharePage");
+
+      let listener = {
+        onWidgetAdded: (aWidgetId) => {
+          if (aWidgetId != this.id)
+            return;
+
+          Services.obs.notifyObservers(null, "social:" + this.id + "-added", null);
+        },
+
+        onWidgetRemoved: aWidgetId => {
+          if (aWidgetId != this.id)
+            return;
+
+          Services.obs.notifyObservers(null, "social:" + this.id + "-removed", null);
+        },
+
+        onWidgetInstanceRemoved: (aWidgetId, aDoc) => {
+          if (aWidgetId != this.id || aDoc != aDocument)
+            return;
+
+          CustomizableUI.removeListener(listener);
+        }
+      };
+      CustomizableUI.addListener(listener);
+
+      return node;
+    }
   }, {
     id: "add-ons-button",
     shortcutId: "key_openAddons",

browser/components/customizableui/content/panelUI.inc.xul

@@ -240,6 +240,8 @@
                      onclick="PanelUI.hide();"/>
     </panelview>
 
+    <panelview id="PanelUI-socialapi" flex="1"/>
+
     <panelview id="PanelUI-feeds" flex="1" oncommand="FeedHandler.subscribeToFeed(null, event);">
       <label value="&feedsMenu2.label;" class="panel-subview-header"/>
     </panelview>