Use "unsigned" rather than "unsigned long" for C++ code interacting with WebIDL's "unsigned long".

Source/modules/mediasource/SourceBufferList.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 33 matching lines @@
     DEFINE_EVENT_TARGET_REFCOUNTING_WILL_BE_REMOVED(RefCountedGarbageCollected<SourceBufferList>);
     DEFINE_WRAPPERTYPEINFO();
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(SourceBufferList);
 public:
     static SourceBufferList* create(ExecutionContext* context, GenericEventQueue* asyncEventQueue)
     {
         return new SourceBufferList(context, asyncEventQueue);
     }
     virtual ~SourceBufferList();
 
-    unsigned long length() const { return m_list.size(); }
-    SourceBuffer* item(unsigned long index) const { return (index < m_list.size()) ? m_list[index].get() : 0; }
+    unsigned length() const { return m_list.size(); }
+    SourceBuffer* item(unsigned index) const { return (index < m_list.size()) ? m_list[index].get() : 0; }
 
     void add(SourceBuffer*);
     void insert(size_t position, SourceBuffer*);
     void remove(SourceBuffer*);
     size_t find(SourceBuffer* buffer) { return m_list.find(buffer); }
     bool contains(SourceBuffer* buffer) { return m_list.find(buffer) != kNotFound; }
     void clear();
 
     // EventTarget interface
     virtual const AtomicString& interfaceName() const override;
     virtual ExecutionContext* executionContext() const override;
 
     virtual void trace(Visitor*) override;
 
 private:
     SourceBufferList(ExecutionContext*, GenericEventQueue*);
 
     void scheduleEvent(const AtomicString&);
 
     ExecutionContext* m_executionContext;
     GenericEventQueue* m_asyncEventQueue;
 
     HeapVector<Member<SourceBuffer> > m_list;
 };
 
 } // namespace blink
 
 #endif // SourceBufferList_h