MSE: Start letting SourceBuffer begin to do initialization segment received algorithm

Source/modules/mediasource/SourceBufferList.cpp

 /*
  * 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 39 matching lines @@
     ASSERT(m_list.isEmpty());
 #endif
 }
 
 void SourceBufferList::add(SourceBuffer* buffer)
 {
     m_list.append(buffer);
     scheduleEvent(EventTypeNames::addsourcebuffer);
 }
 
+void SourceBufferList::insert(size_t position, SourceBuffer* buffer)
+{
+    m_list.insert(position, buffer);
+    scheduleEvent(EventTypeNames::addsourcebuffer);
+}
+
 void SourceBufferList::remove(SourceBuffer* buffer)
 {
     size_t index = m_list.find(buffer);
     if (index == kNotFound)
         return;
     m_list.remove(index);
     scheduleEvent(EventTypeNames::removesourcebuffer);
 }
 
 void SourceBufferList::clear()
@@ skipping 22 matching lines @@
     return m_executionContext;
 }
 
 void SourceBufferList::trace(Visitor* visitor)
 {
     visitor->trace(m_list);
     EventTargetWithInlineData::trace(visitor);
 }
 
 } // namespace blink