BB 42037: Disable about:firefoxview page

browser/base/content/browser.js

@@ -7515,6 +7515,11 @@ var FirefoxViewHandler = {
     }
   },
   openTab(section) {
+    if (AppConstants.BASE_BROWSER_VERSION) {
+      // about:firefoxview is disabled. tor-browser#42037.
+      return;
+    }
+
     if (!CustomizableUI.getPlacementOfWidget(this.BUTTON_ID)) {
       CustomizableUI.addWidgetToArea(
         this.BUTTON_ID,

browser/components/about/AboutRedirector.cpp

@@ -74,9 +74,6 @@ static const RedirEntry kRedirMap[] = {
          nsIAboutModule::URI_CAN_LOAD_IN_PRIVILEGEDABOUT_PROCESS |
          nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT |
          nsIAboutModule::IS_SECURE_CHROME_UI},
-    {"firefoxview", "chrome://browser/content/firefoxview/firefoxview.html",
-     nsIAboutModule::ALLOW_SCRIPT | nsIAboutModule::IS_SECURE_CHROME_UI |
-         nsIAboutModule::HIDE_FROM_ABOUTABOUT},
     {"policies", "chrome://browser/content/policies/aboutPolicies.html",
      nsIAboutModule::ALLOW_SCRIPT | nsIAboutModule::IS_SECURE_CHROME_UI},
     {"privatebrowsing", "chrome://browser/content/aboutPrivateBrowsing.html",

browser/components/about/components.conf

@@ -13,7 +13,6 @@ pages = [
     'home',
     'logins',
     'loginsimportreport',
-    'firefoxview',
     'messagepreview',
     'newtab',
     'pocket-home',

browser/components/moz.build

@@ -40,7 +40,6 @@ DIRS += [
     "downloads",
     "enterprisepolicies",
     "extensions",
-    "firefoxview",
     "genai",
     "messagepreview",
     "migration",

browser/themes/shared/tabbrowser/tabs.css

@@ -1278,8 +1278,13 @@ tab-group {
   color-scheme: var(--tab-selected-color-scheme);
 }
 
-:root:not([privatebrowsingmode], [firefoxviewhidden]) :is(toolbarbutton, toolbarpaletteitem) ~ #tabbrowser-tabs,
-:root[privatebrowsingmode]:not([firefoxviewhidden]) :is(
+/* about:firefoxview is disabled in Base Browser. See tor-browser#42037.
+ * Therefore we always hide #firefox-view-button, regardless of private
+ * browsing. Here we only want to draw the border if there is a non-hidden
+ * toolbar item before the tabs.
+ * NOTE: Expect merge conflict from bugzilla bug 1917595 and bug 1917599. In
+ * these cases we want to keep our selector as-is. */
+:root :is(
   toolbarbutton:not(#firefox-view-button),
   toolbarpaletteitem:not(#wrapper-firefox-view-button)
 ) ~ #tabbrowser-tabs {
@@ -1288,8 +1293,13 @@ tab-group {
   margin-inline-start: 2px;
 }
 
-:root[firefoxviewhidden] :is(#firefox-view-button, #wrapper-firefox-view-button),
-:root[privatebrowsingmode] :is(#firefox-view-button, #menu_openFirefoxView) {
+/* about:firefoxview is disabled in Base Browser. Always hide the toolbar button
+ * and menu item regardless of private browsing. See tor-browser#42037.
+ * NOTE: We also hide #wrapper-firefox-view-button, which is used during
+ * customization.
+ * NOTE: Expect merge conflict from bugzilla bug 1903812 and bug 1917599. In
+ * these cases we want to keep our selector as-is. */
+#firefox-view-button, #wrapper-firefox-view-button, #menu_openFirefoxView {
   display: none;
 }