Bug 803688 - Remove LinkedListElements from their list when they're destructed, and assert that a LinkedList is empty when it's destructed. r=waldo, a=tef+

mfbt/LinkedList.h

@@ -13,6 +13,10 @@
  * LinkedListElement<T>.  A given object may be in only one linked list at a
  * time.
  *
+ * A LinkedListElement automatically removes itself from the list upon
+ * destruction, and a LinkedList will fatally assert in debug builds if it's
+ * non-empty when it's destructed.
+ *
  * For example, you might use LinkedList in a simple observer list class as
  * follows.
  *
@@ -104,6 +108,11 @@ class LinkedListElement
   public:
     LinkedListElement() : next(this), prev(this), isSentinel(false) { }
 
+    ~LinkedListElement() {
+      if (!isSentinel && isInList())
+        remove();
+    }
+
     /*
      * Get the next element in the list, or NULL if this is the last element in
      * the list.
@@ -178,8 +187,7 @@ class LinkedListElement
       : next(this),
         prev(this),
         isSentinel(nodeKind == NODE_KIND_SENTINEL)
-    {
-    }
+    { }
 
     /*
      * Return |this| cast to T* if we're a normal node, or return NULL if we're