Bug 1606390 Convert browser.newtabpage.enabled to a static pref r=Gijs

Converts `browser.newtabpage.enabled` into a static pref. Removes their varcache pref declaration. `signon.management.page.enabled` in the same file will be removed instead (Bug 1606888) as it is no longer needed.

Differential Revision: https://phabricator.services.mozilla.com/D58559

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

browser/app/profile/firefox.js

@@ -1256,9 +1256,6 @@ pref("prompts.tab_modal.enabled", true);
 // Activates preloading of the new tab url.
 pref("browser.newtab.preload", true);
 
-// Indicates if about:newtab shows content (enabled) or just blank
-pref("browser.newtabpage.enabled", true);
-
 // Activity Stream prefs that control to which page to redirect
 #ifndef RELEASE_OR_BETA
   pref("browser.newtabpage.activity-stream.debug", false);

browser/components/about/AboutRedirector.cpp

@@ -12,6 +12,7 @@
 #include "nsIURI.h"
 #include "nsIProtocolHandler.h"
 #include "mozilla/ArrayUtils.h"
+#include "mozilla/StaticPrefs_browser.h"
 #include "mozilla/Preferences.h"
 #include "nsServiceManagerUtils.h"
 
@@ -20,7 +21,6 @@ namespace browser {
 
 NS_IMPL_ISUPPORTS(AboutRedirector, nsIAboutModule)
 
-bool AboutRedirector::sNewTabPageEnabled = false;
 bool AboutRedirector::sAboutLoginsEnabled = false;
 
 static const uint32_t ACTIVITY_STREAM_FLAGS =
@@ -157,13 +157,6 @@ AboutRedirector::NewChannel(nsIURI* aURI, nsILoadInfo* aLoadInfo,
   nsCOMPtr<nsIIOService> ioService = do_GetIOService(&rv);
   NS_ENSURE_SUCCESS(rv, rv);
 
-  static bool sNTPEnabledCacheInited = false;
-  if (!sNTPEnabledCacheInited) {
-    Preferences::AddBoolVarCache(&AboutRedirector::sNewTabPageEnabled,
-                                 "browser.newtabpage.enabled");
-    sNTPEnabledCacheInited = true;
-  }
-
   static bool sAboutLoginsCacheInited = false;
   if (!sAboutLoginsCacheInited) {
     Preferences::AddBoolVarCache(&AboutRedirector::sAboutLoginsEnabled,
@@ -176,9 +169,10 @@ AboutRedirector::NewChannel(nsIURI* aURI, nsILoadInfo* aLoadInfo,
       nsAutoCString url;
 
       // Let the aboutNewTabService decide where to redirect for about:home and
-      // enabled about:newtab. Disabledx about:newtab page uses fallback.
+      // enabled about:newtab. Disabled about:newtab page uses fallback.
       if (path.EqualsLiteral("home") ||
-          (sNewTabPageEnabled && path.EqualsLiteral("newtab"))) {
+          (StaticPrefs::browser_newtabpage_enabled() &&
+           path.EqualsLiteral("newtab"))) {
         nsCOMPtr<nsIAboutNewTabService> aboutNewTabService =
             do_GetService("@mozilla.org/browser/aboutnewtab-service;1", &rv);
         NS_ENSURE_SUCCESS(rv, rv);

browser/components/about/AboutRedirector.h

@@ -25,7 +25,6 @@ class AboutRedirector : public nsIAboutModule {
 
  private:
   static bool sAboutLoginsEnabled;
-  static bool sNewTabPageEnabled;
 };
 
 }  // namespace browser

modules/libpref/init/StaticPrefList.yaml

@@ -885,6 +885,12 @@
   value: false
   mirror: always
 
+# Indicates if about:newtab shows content (enabled) or just blank.
+- name: browser.newtabpage.enabled
+  type: bool
+  value: true
+  mirror: always
+
 # Blocked plugin content
 - name: browser.safebrowsing.blockedURIs.enabled
   type: bool