1 files changed, 62 insertions, 6 deletions

diff --git a/editor/libeditor/EditorBase.h b/editor/libeditor/EditorBase.h
index 7ea0f4dab..618da12a8 100644
--- a/editor/libeditor/EditorBase.h
+++ b/editor/libeditor/EditorBase.h
@@ -17,6 +17,7 @@
 #include "nsCOMPtr.h"                   // for already_AddRefed, nsCOMPtr
 #include "nsCycleCollectionParticipant.h"
 #include "nsGkAtoms.h"
+#include "nsIDocument.h"                // for nsIDocument
 #include "nsIEditor.h"                  // for nsIEditor::EDirection, etc.
 #include "nsIEditorIMESupport.h"        // for NS_DECL_NSIEDITORIMESUPPORT, etc.
 #include "nsIObserver.h"                // for NS_DECL_NSIOBSERVER, etc.
@@ -32,7 +33,6 @@
 
 class nsIAtom;
 class nsIContent;
-class nsIDOMDocument;
 class nsIDOMEvent;
 class nsIDOMEventListener;
 class nsIDOMEventTarget;
@@ -135,6 +135,57 @@ namespace widget {
 struct IMEState;
 } // namespace widget
 
+/**
+ * CachedWeakPtr stores a pointer to a class which inherits nsIWeakReference.
+ * If the instance of the class has already been destroyed, this returns
+ * nullptr.  Otherwise, returns cached pointer.
+ */
+template<class T>
+class CachedWeakPtr final
+{
+public:
+  CachedWeakPtr<T>()
+    : mCache(nullptr)
+  {
+  }
+
+  CachedWeakPtr<T>& operator=(T* aObject)
+  {
+    mWeakPtr = do_GetWeakReference(aObject);
+    mCache = aObject;
+    return *this;
+  }
+  CachedWeakPtr<T>& operator=(const nsCOMPtr<T>& aOther)
+  {
+    mWeakPtr = do_GetWeakReference(aOther);
+    mCache = aOther;
+    return *this;
+  }
+  CachedWeakPtr<T>& operator=(already_AddRefed<T>& aOther)
+  {
+    nsCOMPtr<T> other = aOther;
+    mWeakPtr = do_GetWeakReference(other);
+    mCache = other;
+    return *this;
+  }
+
+  bool IsAlive() const { return mWeakPtr && mWeakPtr->IsAlive(); }
+
+  explicit operator bool() const { return mWeakPtr; }
+  operator T*() const { return get(); }
+  T* get() const
+  {
+    if (mCache && !mWeakPtr->IsAlive()) {
+      const_cast<CachedWeakPtr<T>*>(this)->mCache = nullptr;
+    }
+    return mCache;
+  }
+
+private:
+  nsWeakPtr mWeakPtr;
+  T* MOZ_NON_OWNING_REF mCache;
+};
+
 #define kMOZEditorBogusNodeAttrAtom nsGkAtoms::mozeditorbogusnode
 #define kMOZEditorBogusNodeValue NS_LITERAL_STRING("TRUE")
 
@@ -178,6 +229,7 @@ public:
   NS_DECL_CYCLE_COLLECTING_ISUPPORTS
   NS_DECL_CYCLE_COLLECTION_CLASS_AMBIGUOUS(EditorBase, nsIEditor)
 
+  bool IsInitialized() const { return !!mDocumentWeak; }
   already_AddRefed<nsIDOMDocument> GetDOMDocument();
   already_AddRefed<nsIDocument> GetDocument();
   already_AddRefed<nsIPresShell> GetPresShell();
@@ -848,7 +900,7 @@ public:
 
   bool HasIndependentSelection() const
   {
-    return !!mSelConWeak;
+    return !!mSelectionControllerWeak;
   }
 
   /**
@@ -954,6 +1006,14 @@ public:
     }
   }
 
+private:
+  // Weak reference to the nsISelectionController.
+  // Use GetSelectionController() to retrieve actual pointer.
+  CachedWeakPtr<nsISelectionController> mSelectionControllerWeak;
+  // Weak reference to the nsIDocument.
+  // Use GetDocument() to retrieve actual pointer.
+  CachedWeakPtr<nsIDocument> mDocumentWeak;
+
 protected:
   enum Tristate
   {
@@ -975,12 +1035,8 @@ protected:
   // The form field as an event receiver.
   nsCOMPtr<dom::EventTarget> mEventTarget;
   nsCOMPtr<nsIDOMEventListener> mEventListener;
-  // Weak reference to the nsISelectionController.
-  nsWeakPtr mSelConWeak;
   // Weak reference to placeholder for begin/end batch purposes.
   WeakPtr<PlaceholderTransaction> mPlaceholderTransactionWeak;
-  // Weak reference to the nsIDOMDocument.
-  nsWeakPtr mDocWeak;
   // Name of placeholder transaction.
   nsIAtom* mPlaceholderName;
   // Saved selection state for placeholder transaction batching.