Bug 1763672 - Introduce targetTopLevelLinkClicksToBlank on BrowsingContext. r=nika

This property defaults to false. When set to true, user-initiated link clicks in
the top-level BrowsingContext will default target to _blank. This is similar to what
we do for App Tabs, but is slightly more aggressive in that in will also occur for
same-origin navigations.

Differential Revision: https://phabricator.services.mozilla.com/D143374

docshell/base/CanonicalBrowsingContext.cpp

@@ -317,6 +317,8 @@ void CanonicalBrowsingContext::ReplacedBy(
   // about:blank documents created in it.
   txn.SetSandboxFlags(GetSandboxFlags());
   txn.SetInitialSandboxFlags(GetSandboxFlags());
+  txn.SetTargetTopLevelLinkClicksToBlankInternal(
+      TargetTopLevelLinkClicksToBlank());
   if (aNewContext->EverAttached()) {
     MOZ_ALWAYS_SUCCEEDS(txn.Commit(aNewContext));
   } else {
@@ -2678,6 +2680,12 @@ void CanonicalBrowsingContext::SetTouchEventsOverride(
   SetTouchEventsOverrideInternal(aOverride, aRv);
 }
 
+void CanonicalBrowsingContext::SetTargetTopLevelLinkClicksToBlank(
+    bool aTargetTopLevelLinkClicksToBlank, ErrorResult& aRv) {
+  SetTargetTopLevelLinkClicksToBlankInternal(aTargetTopLevelLinkClicksToBlank,
+                                             aRv);
+}
+
 void CanonicalBrowsingContext::AddPageAwakeRequest() {
   MOZ_ASSERT(IsTop());
   auto count = GetPageAwakeRequestCount();