Bug 1477930 - Remove taggingService HasTags synchronous API. r=Standard8

The tagging API is moving to the bookmarking API, this is part of it.
This will break the tags root open glyph in the Library, for now we don't have
an alternative, we'll re-evaluate in the future in bug 1477934.

Differential Revision: https://phabricator.services.mozilla.com/D2318

--HG--
extra : moz-landing-system : lando

toolkit/components/places/nsITaggingService.idl

@@ -72,13 +72,6 @@ interface nsITaggingService : nsISupports
    * Retrieves all tags used to tag URIs in the data-base (sorted by name).
    */
   readonly attribute nsIVariant allTags;
-
-  /**
-   * Whether any tags exist.
-   *
-   * @note This is faster than allTags.length, since doesn't need to sort tags.
-   */
-  readonly attribute boolean hasTags;
 };
 
 %{C++

toolkit/components/places/nsNavHistoryResult.cpp

@@ -1878,17 +1878,6 @@ nsNavHistoryQueryResultNode::GetHasChildren(bool* aHasChildren)
     return NS_OK;
   }
 
-  // For tag containers query we must check if we have any tag
-  if (resultType == nsINavHistoryQueryOptions::RESULTS_AS_TAGS_ROOT) {
-    nsCOMPtr<nsITaggingService> tagging =
-      do_GetService(NS_TAGGINGSERVICE_CONTRACTID);
-    if (tagging) {
-      bool hasTags;
-      *aHasChildren = NS_SUCCEEDED(tagging->GetHasTags(&hasTags)) && hasTags;
-    }
-    return NS_OK;
-  }
-
   // For history containers query we must check if we have any history
   if (resultType == nsINavHistoryQueryOptions::RESULTS_AS_DATE_QUERY ||
       resultType == nsINavHistoryQueryOptions::RESULTS_AS_DATE_SITE_QUERY ||
@@ -1899,15 +1888,18 @@ nsNavHistoryQueryResultNode::GetHasChildren(bool* aHasChildren)
     return NS_OK;
   }
 
-  //XXX: For other containers queries we must:
-  // 1. If it's open, just check mChildren for containers
-  // 2. Else null the view (keep it in a var), open container, check mChildren
-  //    for containers, close container, reset the view
+  // TODO (Bug 1477934): We don't have a good synchronous way to fetch whether
+  // we have tags or not, to properly reply to the hasChildren request on the
+  // tags root. Potentially we could pass this information when we create the
+  // container.
 
+  // If the container is open and populated, this is trivial.
   if (mContentsValid) {
     *aHasChildren = (mChildren.Count() > 0);
     return NS_OK;
   }
+
+  // Fallback to assume we have children.
   *aHasChildren = true;
   return NS_OK;
 }

toolkit/components/places/nsTaggingService.js

@@ -325,11 +325,6 @@ TaggingService.prototype = {
     return this.__tagFolders;
   },
 
-  // nsITaggingService
-  get hasTags() {
-    return this._tagFolders.length > 0;
-  },
-
   // nsIObserver
   observe: function TS_observe(aSubject, aTopic, aData) {
     if (aTopic == TOPIC_SHUTDOWN) {