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

(WebIDL's "unsigned long" is a 32-bit type)

BUG=267360

Review URL: https://codereview.chromium.org/721053002

git-svn-id: svn://svn.chromium.org/blink/trunk@185283 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/modules/mediasource/SourceBufferList.h

@@ -51,8 +51,8 @@ public:
     }
     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*);