Bug 1662841: Remove Fission-incompatible `nsDocumentViewer::AppendSubtree`. r=nika

Differential Revision: https://phabricator.services.mozilla.com/D90615

docshell/base/nsIContentViewer.idl

@@ -32,7 +32,6 @@ class WindowGlobalChild;
 [ptr] native nsPresContextPtr(nsPresContext);
 [ptr] native nsViewPtr(nsView);
 [ptr] native nsDOMNavigationTimingPtr(nsDOMNavigationTiming);
-[ref] native nsIContentViewerTArray(nsTArray<nsCOMPtr<nsIContentViewer> >);
 [ptr] native Encoding(const mozilla::Encoding);
 [ptr] native PresShellPtr(mozilla::PresShell);
 [ptr] native WindowGlobalChildPtr(mozilla::dom::WindowGlobalChild);
@@ -288,12 +287,6 @@ interface nsIContentViewer : nsISupports
   void getContentSizeConstrained(in long maxWidth, in long maxHeight,
                                  out long width, out long height);
 
-  /**
-   * Append |this| and all of its descendants to the given array,
-   * in depth-first pre-order traversal.
-   */
-  [noscript] void appendSubtree(in nsIContentViewerTArray array);
-
   /**
    * Instruct the refresh driver to discontinue painting until further
    * notice.

docshell/base/nsIDocShell.idl

@@ -165,7 +165,7 @@ interface nsIDocShell : nsIDocShellTreeItem
    * Content Viewer that is currently loaded for this DocShell.  This may
    * change as the underlying content changes.
    */
-  readonly attribute nsIContentViewer contentViewer;
+  [infallible] readonly attribute nsIContentViewer contentViewer;
 
   /**
    * Get the id of the outer window that is or will be in this docshell.

docshell/base/nsIDocShellTreeItem.idl

@@ -121,7 +121,7 @@ interface nsIDocShellTreeItem : nsISupports
 	@deprecated: Prefer using `BrowsingContext::Children()`, as this count will
 	not include out-of-process iframes.
 	*/
-	[binaryname(InProcessChildCount)]
+	[binaryname(InProcessChildCount), infallible]
 	readonly attribute long childCount;
 
 	/*

layout/base/PresShell.cpp

@@ -11123,6 +11123,23 @@ void PresShell::MarkFixedFramesForReflow(IntrinsicDirty aIntrinsicDirty) {
   }
 }
 
+static void AppendSubtree(nsIDocShell* aDocShell,
+                          nsTArray<nsCOMPtr<nsIContentViewer>>& aArray) {
+  if (nsCOMPtr<nsIContentViewer> cv = aDocShell->GetContentViewer()) {
+    aArray.AppendElement(cv);
+  }
+
+  int32_t n = aDocShell->GetInProcessChildCount();
+  for (int32_t i = 0; i < n; i++) {
+    nsCOMPtr<nsIDocShellTreeItem> childItem;
+    aDocShell->GetInProcessChildAt(i, getter_AddRefs(childItem));
+    if (childItem) {
+      nsCOMPtr<nsIDocShell> child(do_QueryInterface(childItem));
+      AppendSubtree(child, aArray);
+    }
+  }
+}
+
 void PresShell::MaybeReflowForInflationScreenSizeChange() {
   nsPresContext* pc = GetPresContext();
   const bool fontInflationWasEnabled = FontSizeInflationEnabled();
@@ -11137,13 +11154,8 @@ void PresShell::MaybeReflowForInflationScreenSizeChange() {
     return;
   }
   if (nsCOMPtr<nsIDocShell> docShell = pc->GetDocShell()) {
-    nsCOMPtr<nsIContentViewer> cv;
-    docShell->GetContentViewer(getter_AddRefs(cv));
-    if (!cv) {
-      return;
-    }
     nsTArray<nsCOMPtr<nsIContentViewer>> array;
-    cv->AppendSubtree(array);
+    AppendSubtree(docShell, array);
     for (uint32_t i = 0, iEnd = array.Length(); i < iEnd; ++i) {
       nsCOMPtr<nsIContentViewer> cv = array[i];
       if (RefPtr<PresShell> descendantPresShell = cv->GetPresShell()) {

layout/base/nsDocumentViewer.cpp

@@ -2774,16 +2774,6 @@ nsDocumentViewer::SetHintCharset(const Encoding* aEncoding) {
   CallChildren(childFn);
 }
 
-NS_IMETHODIMP nsDocumentViewer::AppendSubtree(
-    nsTArray<nsCOMPtr<nsIContentViewer>>& aArray) {
-  aArray.AppendElement(this);
-  auto childFn = [&aArray](nsDocumentViewer* aChild) {
-    aChild->AppendSubtree(aArray);
-  };
-  CallChildren(childFn);
-  return NS_OK;
-}
-
 NS_IMETHODIMP
 nsDocumentViewer::PausePainting() {
   CallChildren([](nsDocumentViewer* aChild) { aChild->PausePainting(); });