Bug 760342 - Check explicitly for mis-use of HashTable::Enum; r=luke

If a user does removeFront or rekeyFront on an Enum, then continues to use it,
it will fail, potentially randomly. This patch makes the failure explicit in
debug builds.

js/public/HashTable.h

@@ -142,21 +142,23 @@ class HashTable : private AllocPolicy
       protected:
         friend class HashTable;
 
-        Range(Entry *c, Entry *e) : cur(c), end(e) {
+        Range(Entry *c, Entry *e) : cur(c), end(e), validEntry(true) {
             while (cur < end && !cur->isLive())
                 ++cur;
         }
 
         Entry *cur, *end;
+        DebugOnly<bool> validEntry;
 
       public:
-        Range() : cur(NULL), end(NULL) {}
+        Range() : cur(NULL), end(NULL), validEntry(false) {}
 
         bool empty() const {
             return cur == end;
         }
 
         T &front() const {
+            JS_ASSERT(validEntry);
             JS_ASSERT(!empty());
             return cur->t;
         }
@@ -165,6 +167,7 @@ class HashTable : private AllocPolicy
             JS_ASSERT(!empty());
             while (++cur < end && !cur->isLive())
                 continue;
+            validEntry = true;
         }
     };
 
@@ -205,6 +208,7 @@ class HashTable : private AllocPolicy
         void removeFront() {
             table.remove(*this->cur);
             removed = true;
+            this->validEntry = false;
         }
 
         /*
@@ -221,6 +225,7 @@ class HashTable : private AllocPolicy
             table.remove(*this->cur);
             table.add(l, e);
             added = true;
+            this->validEntry = false;
         }
 
         void rekeyFront(const Key &k) {

js/src/jsweakmap.h

@@ -187,7 +187,6 @@ class WeakMap : public HashMap<Key, Value, HashPolicy, RuntimeAllocPolicy>, publ
                     markedAny = true;
                 e.rekeyFront(k);
             }
-            JS_ASSERT_IF(keyIsMarked, gc::IsMarked(&e.front().value));
         }
         return markedAny;
     }