Bug 1632116 - Introduce dom.window.content.untrusted.enabled r=emilio

`window.content` is currently disabled only in Nightly by C preprecessor, and this patch replaces it with a new flag to allow users to manipulate.

Differential Revision: https://phabricator.services.mozilla.com/D71775

dom/base/nsGlobalWindowInner.cpp

@@ -2918,8 +2918,7 @@ void nsGlobalWindowInner::GetOwnPropertyNames(
 }
 
 /* static */
-bool nsGlobalWindowInner::IsPrivilegedChromeWindow(JSContext* aCx,
-                                                   JSObject* aObj) {
+bool nsGlobalWindowInner::IsPrivilegedChromeWindow(JSContext*, JSObject* aObj) {
   // For now, have to deal with XPConnect objects here.
   nsGlobalWindowInner* win = xpc::WindowOrNull(aObj);
   return win && win->IsChromeWindow() &&
@@ -2929,17 +2928,23 @@ bool nsGlobalWindowInner::IsPrivilegedChromeWindow(JSContext* aCx,
 
 /* static */
 bool nsGlobalWindowInner::IsRequestIdleCallbackEnabled(JSContext* aCx,
-                                                       JSObject* aObj) {
+                                                       JSObject*) {
   // The requestIdleCallback should always be enabled for system code.
   return StaticPrefs::dom_requestIdleCallback_enabled() ||
          nsContentUtils::IsSystemCaller(aCx);
 }
 
 /* static */
-bool nsGlobalWindowInner::DeviceSensorsEnabled(JSContext* aCx, JSObject* aObj) {
+bool nsGlobalWindowInner::DeviceSensorsEnabled(JSContext*, JSObject*) {
   return Preferences::GetBool("device.sensors.enabled");
 }
 
+/* static */
+bool nsGlobalWindowInner::ContentPropertyEnabled(JSContext* aCx, JSObject*) {
+  return StaticPrefs::dom_window_content_untrusted_enabled() ||
+         nsContentUtils::IsSystemCaller(aCx);
+}
+
 nsDOMOfflineResourceList* nsGlobalWindowInner::GetApplicationCache(
     ErrorResult& aError) {
   if (!mApplicationCache) {

dom/base/nsGlobalWindowInner.h

@@ -386,12 +386,13 @@ class nsGlobalWindowInner final : public mozilla::dom::EventTarget,
   mozilla::dom::Nullable<mozilla::dom::WindowProxyHolder> IndexedGetter(
       uint32_t aIndex);
 
-  static bool IsPrivilegedChromeWindow(JSContext* /* unused */, JSObject* aObj);
+  static bool IsPrivilegedChromeWindow(JSContext*, JSObject* aObj);
 
-  static bool IsRequestIdleCallbackEnabled(JSContext* aCx,
-                                           JSObject* /* unused */);
+  static bool IsRequestIdleCallbackEnabled(JSContext* aCx, JSObject*);
 
-  static bool DeviceSensorsEnabled(JSContext* /* unused */, JSObject* aObj);
+  static bool DeviceSensorsEnabled(JSContext*, JSObject*);
+
+  static bool ContentPropertyEnabled(JSContext* aCx, JSObject*);
 
   bool DoResolve(JSContext* aCx, JS::Handle<JSObject*> aObj,
                  JS::Handle<jsid> aId,

dom/webidl/Window.webidl

@@ -502,10 +502,7 @@ partial interface Window {
                                                optional DOMString options = "",
                                                any... extraArguments);
 
-  [
-#ifdef NIGHTLY_BUILD
-   ChromeOnly,
-#endif
+  [Func="nsGlobalWindowInner::ContentPropertyEnabled",
    NonEnumerable, Replaceable, Throws, NeedsCallerType]
   readonly attribute object? content;
 

modules/libpref/init/StaticPrefList.yaml

@@ -3103,6 +3103,11 @@
   value: true
   mirror: always
 
+- name: dom.window.content.untrusted.enabled
+  type: bool
+  value: @IS_NOT_NIGHTLY_BUILD@
+  mirror: always
+
 - name: dom.worker.canceling.timeoutMilliseconds
   type: RelaxedAtomicUint32
   value: 30000    # 30 seconds