Bug 1842030 - Part 1: Adding CanonicalBrowsingContext::IsPrivateBrowsingActive(). r=nika

The CanonicalBrowsingContext::IsPrivateBrowsingActive() function allows
us to know if private browsing is active. We need it to prevent setting
cookies if there is no active private browsing session.

Differential Revision: https://phabricator.services.mozilla.com/D184010

docshell/base/CanonicalBrowsingContext.cpp

@@ -1351,6 +1351,11 @@ uint32_t CanonicalBrowsingContext::CountSiteOrigins(
   return uniqueSiteOrigins.Count();
 }
 
+/* static */
+bool CanonicalBrowsingContext::IsPrivateBrowsingActive() {
+  return gNumberOfPrivateContexts > 0;
+}
+
 void CanonicalBrowsingContext::UpdateMediaControlAction(
     const MediaControlAction& aAction) {
   if (IsDiscarded()) {

docshell/base/CanonicalBrowsingContext.h

@@ -201,6 +201,9 @@ class CanonicalBrowsingContext final : public BrowsingContext {
       GlobalObject& aGlobal,
       const Sequence<mozilla::OwningNonNull<BrowsingContext>>& aRoots);
 
+  // Return true if a private browsing session is active.
+  static bool IsPrivateBrowsingActive();
+
   // This function would propogate the action to its all child browsing contexts
   // in content processes.
   void UpdateMediaControlAction(const MediaControlAction& aAction);