Bug 1597482 - Replace nsIDocShellTreeItem with BrowsingContext in GetProfileTimelineSubDocShells. r=mstange

`GetProfileTimelineSubDocShells` was using nsIDocShellTreeItem to walk the
DocShells that are visible and recording profile markers. This change switches
to using `BrowsingContext` for the walk, and ignores OOP iframes as they aren't
painting in the current process.

Differential Revision: https://phabricator.services.mozilla.com/D63960

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

layout/base/nsRefreshDriver.cpp

@@ -1592,29 +1592,27 @@ static void GetProfileTimelineSubDocShells(nsDocShell* aRootDocShell,
     return;
   }
 
-  nsTArray<RefPtr<nsIDocShell>> docShells;
+  RefPtr<BrowsingContext> bc = aRootDocShell->GetBrowsingContext();
-  nsresult rv = aRootDocShell->GetAllDocShellsInSubtree(
+  if (!bc) {
-      nsIDocShellTreeItem::typeAll, nsIDocShell::ENUMERATE_BACKWARDS,
-      docShells);
-
-  if (NS_FAILED(rv)) {
     return;
   }
 
-  for (const auto& curItem : docShells) {
+  bc->PostOrderWalk([&](BrowsingContext* aContext) {
-    if (!curItem->GetRecordProfileTimelineMarkers()) {
+    nsDocShell* shell = nsDocShell::Cast(aContext->GetDocShell());
-      continue;
+    if (!shell || !shell->GetRecordProfileTimelineMarkers()) {
+      // This process isn't painting OOP iframes so we ignore
+      // docshells that are OOP.
+      return;
     }
 
-    nsDocShell* shell = static_cast<nsDocShell*>(curItem.get());
     bool isVisible = false;
     shell->GetVisibility(&isVisible);
     if (!isVisible) {
-      continue;
+      return;
     }
 
     aShells.AppendElement(shell);
-  }
+  });
 }
 
 static void TakeFrameRequestCallbacksFrom(