Bug 1572505 - Convert network.dns.disablePrefetchFromHTTPS to static pref. r=smaug,njn

Converts network.dns.disablePrefetchFromHTTPS to a static pref. Though the original VarCache pref default to `false`, it looks like the intended value is `true`. (see comment #0 in bug 1572505)

Differential Revision: https://phabricator.services.mozilla.com/D42737

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

dom/base/Document.cpp

@@ -34,6 +34,7 @@
 #include "mozilla/StaticPrefs_dom.h"
 #include "mozilla/StaticPrefs_full_screen_api.h"
 #include "mozilla/StaticPrefs_layout.h"
+#include "mozilla/StaticPrefs_network.h"
 #include "mozilla/StaticPrefs_page_load.h"
 #include "mozilla/StaticPrefs_plugins.h"
 #include "mozilla/StaticPrefs_privacy.h"
@@ -351,8 +352,6 @@
 
 #define NS_MAX_DOCUMENT_WRITE_DEPTH 20
 
-extern bool sDisablePrefetchHTTPSPref;
-
 mozilla::LazyLogModule gPageCacheLog("PageCache");
 
 namespace mozilla {
@@ -3495,7 +3494,8 @@ void Document::RemoveFromIdTable(Element* aElement, nsAtom* aId) {
 void Document::SetPrincipals(nsIPrincipal* aNewPrincipal,
                              nsIPrincipal* aNewStoragePrincipal) {
   MOZ_ASSERT(!!aNewPrincipal == !!aNewStoragePrincipal);
-  if (aNewPrincipal && mAllowDNSPrefetch && sDisablePrefetchHTTPSPref) {
+  if (aNewPrincipal && mAllowDNSPrefetch &&
+      StaticPrefs::network_dns_disablePrefetchFromHTTPS()) {
     nsCOMPtr<nsIURI> uri;
     aNewPrincipal->GetURI(getter_AddRefs(uri));
     if (!uri || uri->SchemeIs("https")) {

dom/html/nsHTMLDNSPrefetch.cpp

@@ -38,7 +38,6 @@ using namespace mozilla::dom;
 using namespace mozilla::net;
 
 static NS_DEFINE_CID(kDNSServiceCID, NS_DNSSERVICE_CID);
-bool sDisablePrefetchHTTPSPref;
 static bool sInitialized = false;
 static nsIDNSService* sDNSService = nullptr;
 static nsHTMLDNSPrefetch::nsDeferrals* sPrefetches = nullptr;
@@ -59,15 +58,8 @@ nsresult nsHTMLDNSPrefetch::Initialize() {
 
   sPrefetches->Activate();
 
-  Preferences::AddBoolVarCache(&sDisablePrefetchHTTPSPref,
-                               "network.dns.disablePrefetchFromHTTPS");
-
   Preferences::AddBoolVarCache(&sEsniEnabled, "network.security.esni.enabled");
 
-  // Default is false, so we need an explicit call to prime the cache.
-  sDisablePrefetchHTTPSPref =
-      Preferences::GetBool("network.dns.disablePrefetchFromHTTPS", true);
-
   sEsniEnabled = Preferences::GetBool("network.security.esni.enabled", false);
 
   NS_IF_RELEASE(sDNSService);

modules/libpref/init/StaticPrefList.yaml

@@ -5985,6 +5985,11 @@
   value: 0
   mirror: always
 
+- name: network.dns.disablePrefetchFromHTTPS
+  type: bool
+  value: true
+  mirror: always
+
 # Max time to shutdown the resolver threads
 - name: network.dns.resolver_shutdown_timeout_ms
   type: uint32_t