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

public/platform/WebSourceBufferClient.h

Index: public/platform/WebSourceBufferClient.h
diff --git a/public/platform/WebSourceBufferClient.h b/public/platform/WebSourceBufferClient.h
new file mode 100644
index 0000000000000000000000000000000000000000..849f2824bac215a5f44ac48dda0319e928ed3d7f
--- /dev/null
+++ b/public/platform/WebSourceBufferClient.h
@@ -0,0 +1,20 @@
+// Copyright 2014 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 WebSourceBufferClient_h
+#define WebSourceBufferClient_h
+
+namespace blink {
+
+class WebSourceBufferClient {
+public:
+    virtual ~WebSourceBufferClient() { }
+
+    // FIXME: Add a track collection parameter here.
+    virtual void initializationSegmentReceived() = 0;
+};
+
+} // namespace blink
+
+#endif // WebSourceBufferClient_h