Bug 1618102 - Use BrowsingContext for Full screen API "is caller in focused tab?" check. r=farre

Differential Revision: https://phabricator.services.mozilla.com/D64288

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

dom/base/Document.cpp

@@ -13429,6 +13429,15 @@ static bool IsInActiveTab(Document* aDoc) {
     return false;
   }
 
+  nsFocusManager* fm = nsFocusManager::GetFocusManager();
+  if (!fm) {
+    return false;
+  }
+
+  if (XRE_IsParentProcess()) {
+    // Keep dom/tests/mochitest/chrome/test_MozDomFullscreen_event.xhtml happy
+    // by retaining the old code path for the parent process.
+
     nsCOMPtr<nsIDocShellTreeItem> rootItem;
     docshell->GetInProcessRootTreeItem(getter_AddRefs(rootItem));
     if (!rootItem) {
@@ -13439,13 +13448,8 @@ static bool IsInActiveTab(Document* aDoc) {
       return false;
     }
 
-  nsIFocusManager* fm = nsFocusManager::GetFocusManager();
-  if (!fm) {
-    return false;
-  }
-
-  nsCOMPtr<mozIDOMWindowProxy> activeWindow;
-  fm->GetActiveWindow(getter_AddRefs(activeWindow));
+    nsCOMPtr<nsPIDOMWindowOuter> activeWindow;
+    activeWindow = fm->GetActiveWindow();
     if (!activeWindow) {
       return false;
     }
@@ -13453,6 +13457,19 @@ static bool IsInActiveTab(Document* aDoc) {
     return activeWindow == rootWin;
   }
 
+  BrowsingContext* bc = aDoc->GetBrowsingContext();
+  if (!bc) {
+    return false;
+  }
+
+  BrowsingContext* activeBrowsingContext = fm->GetActiveBrowsingContext();
+  if (!activeBrowsingContext) {
+    return false;
+  }
+
+  return activeBrowsingContext == bc->Top();
+}
+
 void Document::RemoteFrameFullscreenChanged(Element* aFrameElement) {
   // Ensure the frame element is the fullscreen element in this document.
   // If the frame element is already the fullscreen element in this document,