Adds some debugging code in hopes of tracking down a...

base/id_map.h

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_ID_MAP_H__
 #define BASE_ID_MAP_H__
 
 #include "base/basictypes.h"
 #include "base/hash_tables.h"
 #include "base/logging.h"
@@ skipping 10 matching lines @@
 class IDMap {
  private:
   typedef base::hash_map<int32, T*> HashTable;
   typedef typename HashTable::iterator iterator;
 
  public:
   // support const iterators over the items
   // Note, use iterator->first to get the ID, iterator->second to get the T*
   typedef typename HashTable::const_iterator const_iterator;
 
-  IDMap() : next_id_(1) {
+  IDMap() : next_id_(1), check_on_null_data_(false) {
   }
-  IDMap(const IDMap& other) : next_id_(other.next_id_),
-                                        data_(other.data_) {
+  IDMap(const IDMap& other)
+      : next_id_(other.next_id_),
+        data_(other.data_),
+        check_on_null_data_(other.check_on_null_data_) {
   }
 
+  // Sets whether Add should CHECK if passed in NULL data. Default is false.
+  void set_check_on_null_data(bool value) { check_on_null_data_ = value; }
+
   const_iterator begin() const {
     return data_.begin();
   }
   const_iterator end() const {
     return data_.end();
   }
 
   // Adds a view with an automatically generated unique ID. See AddWithID.
   int32 Add(T* data) {
+    CHECK(!check_on_null_data_ || data);
     int32 this_id = next_id_;
     DCHECK(data_.find(this_id) == data_.end()) << "Inserting duplicate item";
     data_[this_id] = data;
     next_id_++;
     return this_id;
   }
 
   // Adds a new data member with the specified ID. The ID must not be in
   // the list. The caller either must generate all unique IDs itself and use
   // this function, or allow this object to generate IDs and call Add. These
   // two methods may not be mixed, or duplicate IDs may be generated
   void AddWithID(T* data, int32 id) {
+    CHECK(!check_on_null_data_ || data);
     DCHECK(data_.find(id) == data_.end()) << "Inserting duplicate item";
     data_[id] = data;
   }
 
   void Remove(int32 id) {
     iterator i = data_.find(id);
     if (i == data_.end()) {
       NOTREACHED() << "Attempting to remove an item not in the list";
       return;
     }
@@ skipping 13 matching lines @@
 
   size_t size() const {
     return data_.size();
   }
 
  protected:
   // The next ID that we will return from Add()
   int32 next_id_;
 
   HashTable data_;
+
+ private:
+  // See description above setter.
+  bool check_on_null_data_;
 };
 
 #endif  // BASE_ID_MAP_H__