fixup! Bug 7494: Create local home page for TBB.

Bug 41717: Show the bookmarks toolbar on "about:tor" pages as well.

Also an implementation note to AboutNewTabService.

browser/base/content/browser-places.js

@@ -1419,6 +1419,14 @@ var BookmarkingUI = {
   },
 
   isOnNewTabPage({ currentURI }) {
+    // If uri is "about:tor" then we return true. See tor-browser#41717.
+    // NOTE: "about:newtab", "about:welcome", "about:home" and
+    // "about:privatebrowsing" can also redirect to "about:tor".
+    // NOTE: We do not simply add "about:tor" to newTabURLs below because this
+    // would also match "about:torconnect".
+    if (currentURI?.scheme === "about" && currentURI?.filePath === "tor") {
+      return true;
+    }
     // Prevent loading AboutNewTab.jsm during startup path if it
     // is only the newTabURL getter we are interested in.
     let newTabURL = Cu.isModuleLoaded("resource:///modules/AboutNewTab.jsm")

browser/components/newtab/AboutNewTabService.jsm

@@ -430,6 +430,18 @@ class BaseAboutNewTabService {
    * the newtab page has no effect on the result of this function.
    */
   get defaultURL() {
+    // NOTE: We return "about:tor" rather than the "chrome:" path
+    // "chrome://browser/content/abouttor/aboutTor.html"
+    // The result is that the channel created in NewChannel in
+    // browser/components/about/AboutRedirector.cpp will have its
+    // resultPrincipalURI set to "about:tor".
+    // What this means in practice is that the loaded document's documentURI and
+    // currentURI will be "about:tor" rather than "about:newtab", "about:home",
+    // "about:welcome" or "about:privatebrowsing".
+    // The disadvantage of this is that we often need to add "about:tor" to
+    // places where "about:newtab" or other URIs appear.
+    // The advantage is that we maintain more control against changes in
+    // mozilla-central.
     return "about:tor";
   }