Bug 1276857 - Shutdown an accessible if cannot be inserted into the tree, r=yzen

accessible/generic/Accessible-inl.h

@@ -11,6 +11,10 @@
 #include "ARIAMap.h"
 #include "nsCoreUtils.h"
 
+#ifdef A11Y_LOG
+#include "Logging.h"
+#endif
+
 namespace mozilla {
 namespace a11y {
 
@@ -76,6 +80,30 @@ Accessible::ScrollTo(uint32_t aHow) const
     nsCoreUtils::ScrollTo(mDoc->PresShell(), mContent, aHow);
 }
 
+inline bool
+Accessible::InsertAfter(Accessible* aNewChild, Accessible* aRefChild)
+{
+  MOZ_ASSERT(aNewChild, "No new child to insert");
+
+  if (aRefChild && aRefChild->Parent() != this) {
+#ifdef A11Y_LOG
+    logging::TreeInfo("broken accessible tree", 0,
+                      "parent", this, "prev sibling parent",
+                      aRefChild->Parent(), "child", aNewChild, nullptr);
+    if (logging::IsEnabled(logging::eVerbose)) {
+      logging::Tree("TREE", "Document tree", mDoc);
+      logging::DOMTree("TREE", "DOM document tree", mDoc);
+    }
+#endif
+    MOZ_ASSERT_UNREACHABLE("Broken accessible tree");
+    mDoc->UnbindFromDocument(aNewChild);
+    return false;
+  }
+
+  return InsertChildAt(aRefChild ? aRefChild->IndexInParent() + 1 : 0,
+                       aNewChild);
+}
+
 } // namespace a11y
 } // namespace mozilla
 

accessible/generic/Accessible.cpp

@@ -18,7 +18,6 @@
 #include "nsTextEquivUtils.h"
 #include "DocAccessibleChild.h"
 #include "EventTree.h"
-#include "Logging.h"
 #include "Relation.h"
 #include "Role.h"
 #include "RootAccessible.h"

accessible/generic/Accessible.h

@@ -393,12 +393,12 @@ public:
     { return InsertChildAt(mChildren.Length(), aChild); }
   virtual bool InsertChildAt(uint32_t aIndex, Accessible* aChild);
 
-  bool InsertAfter(Accessible* aNewChild, Accessible* aRefChild)
-  {
-    MOZ_ASSERT(aNewChild, "No new child to insert");
-    return InsertChildAt(aRefChild ? aRefChild->IndexInParent() + 1 : 0,
-                         aNewChild);
-  }
+  /**
+   * Inserts a child after given sibling. If the child cannot be inserted,
+   * then the child is unbound from the document, and false is returned. Make
+   * sure to null out any references on the child object as it may be destroyed.
+   */
+  bool InsertAfter(Accessible* aNewChild, Accessible* aRefChild);
 
   virtual bool RemoveChild(Accessible* aChild);
 

accessible/generic/DocAccessible.cpp

@@ -1681,6 +1681,12 @@ public:
    */
   bool Next();
 
+  void Rejected()
+  {
+    mChild = nullptr;
+    mChildBefore = nullptr;
+  }
+
 private:
   Accessible* mChild;
   Accessible* mChildBefore;
@@ -1815,6 +1821,7 @@ DocAccessible::ProcessContentInserted(Accessible* aContainer,
     }
 
     MOZ_ASSERT_UNREACHABLE("accessible was rejected");
+    iter.Rejected();
   } while (iter.Next());
 
   mt.Done();
@@ -1852,7 +1859,9 @@ DocAccessible::ProcessContentInserted(Accessible* aContainer, nsIContent* aNode)
 
     if (child) {
       TreeMutation mt(aContainer);
-      aContainer->InsertAfter(child, walker.Prev());
+      if (!aContainer->InsertAfter(child, walker.Prev())) {
+        return;
+      }
       mt.AfterInsertion(child);
       mt.Done();