Bug 1834274 - Part 1: Implement nsIRFPService.idl for nsRFPService. r=emilio

To allow remote settings client to set fingerprinting overrides from
Javascript, we need to implement nsIRFPService for nsRFPService.

This patch changes the return format of nsRFPService::GetOrCreate() to
match the singleton implementation of nsIRFPService. As a result of it,
we need to change the first init call in nsContentUtils because we
cannot forward a already_AddRefed<> to mozilla::Unused. It will cause a
memory leak.

Differential Revision: https://phabricator.services.mozilla.com/D182809

dom/base/nsContentUtils.cpp

@@ -825,7 +825,8 @@ nsresult nsContentUtils::Init() {
 
   Element::InitCCCallbacks();
 
-  Unused << nsRFPService::GetOrCreate();
+  RefPtr<nsRFPService> rfpService = nsRFPService::GetOrCreate();
+  MOZ_ASSERT(rfpService);
 
   if (XRE_IsParentProcess()) {
     AsyncPrecreateStringBundles();

toolkit/components/resistfingerprinting/components.conf

@@ -0,0 +1,20 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+Classes = [
+    {
+        'name': 'RFPService',
+        'cid': '{20093b2e-d5d5-4ce0-8355-96b8d2dc7ff5}',
+        'interfaces': ['nsIRFPService'],
+        'contract_ids': ['@mozilla.org/rfp-service;1'],
+        'type': 'mozilla::nsRFPService',
+        'headers': ['/toolkit/components/resistfingerprinting/nsRFPService.h'],
+        'singleton': True,
+        'constructor': 'mozilla::nsRFPService::GetOrCreate',
+        'js_name': 'rfp',
+        'processes': ProcessSelector.MAIN_PROCESS_ONLY,
+    },
+]

toolkit/components/resistfingerprinting/moz.build

@@ -26,3 +26,13 @@ EXPORTS.mozilla += [
 EXTRA_JS_MODULES += [
     "RFPHelper.sys.mjs",
 ]
+
+XPIDL_MODULE = "toolkit_resistfingerprinting"
+
+XPCOM_MANIFESTS += [
+    "components.conf",
+]
+
+XPIDL_SOURCES += [
+    "nsIRFPService.idl",
+]

toolkit/components/resistfingerprinting/nsIRFPService.idl

@@ -0,0 +1,13 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+/**
+ * The singleton serivce which handles fingerprinting protection stuffs.
+ */
+[scriptable, builtinclass, uuid(20093b2e-d5d5-4ce0-8355-96b8d2dc7ff5)]
+interface nsIRFPService : nsISupports
+{
+};

toolkit/components/resistfingerprinting/nsRFPService.cpp

@@ -112,7 +112,7 @@ const RFPTarget kDefaultFingerintingProtections =
 // ============================================================================
 // Structural Stuff & Pref Observing
 
-NS_IMPL_ISUPPORTS(nsRFPService, nsIObserver)
+NS_IMPL_ISUPPORTS(nsRFPService, nsIObserver, nsIRFPService)
 
 static StaticRefPtr<nsRFPService> sRFPService;
 static bool sInitialized = false;
@@ -121,7 +121,7 @@ static bool sInitialized = false;
 static Atomic<RFPTarget> sEnabledFingerintingProtections;
 
 /* static */
-nsRFPService* nsRFPService::GetOrCreate() {
+already_AddRefed<nsRFPService> nsRFPService::GetOrCreate() {
   if (!sInitialized) {
     sRFPService = new nsRFPService();
     nsresult rv = sRFPService->Init();
@@ -135,7 +135,7 @@ nsRFPService* nsRFPService::GetOrCreate() {
     sInitialized = true;
   }
 
-  return sRFPService;
+  return do_AddRef(sRFPService);
 }
 
 static const char* gCallbackPrefs[] = {

toolkit/components/resistfingerprinting/nsRFPService.h

@@ -16,6 +16,7 @@
 #include "nsICookieJarSettings.h"
 #include "nsIObserver.h"
 #include "nsISupports.h"
+#include "nsIRFPService.h"
 #include "nsStringFwd.h"
 
 // Defines regarding spoofed values of Navigator object. These spoofed values
@@ -157,12 +158,13 @@ MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(RFPTarget);
 
 // ============================================================================
 
-class nsRFPService final : public nsIObserver {
+class nsRFPService final : public nsIObserver, public nsIRFPService {
  public:
   NS_DECL_ISUPPORTS
   NS_DECL_NSIOBSERVER
+  NS_DECL_NSIRFPSERVICE
 
-  static nsRFPService* GetOrCreate();
+  static already_AddRefed<nsRFPService> GetOrCreate();
 
   // _Rarely_ you will need to know if RFP is enabled, or if FPP is enabled.
   // 98% of the time you should use nsContentUtils::ShouldResistFingerprinting

tools/lint/eslint/eslint-plugin-mozilla/lib/services.json

@@ -41,6 +41,7 @@
   "nsIProperties": "dirsvc",
   "nsIPropertyBag2": "sysinfo",
   "nsIQuotaManagerService": "qms",
+  "nsIRFPService": "rfp",
   "nsIScriptSecurityManager": "scriptSecurityManager",
   "nsISearchService": "search",
   "nsISessionStorageService": "sessionStorage",