Update EME MediaKeyNeededEvent.initData for ISO BMFF to match current spec.

media/mp4/box_reader.h

 // Copyright (c) 2012 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 MEDIA_MP4_BOX_READER_H_
 #define MEDIA_MP4_BOX_READER_H_
 
 #include <map>
 #include <vector>
 
@@ skipping 36 matching lines @@
   bool ReadVec(std::vector<uint8>* t, int count) WARN_UNUSED_RESULT;
 
   // These variants read a 4-byte integer of the corresponding signedness and
   // store it in the 8-byte return type.
   bool Read4Into8(uint64* v) WARN_UNUSED_RESULT;
   bool Read4sInto8s(int64* v) WARN_UNUSED_RESULT;
 
   // Advance the stream by this many bytes.
   bool SkipBytes(int nbytes) WARN_UNUSED_RESULT;
 
-  int size() { return size_; }
-  int pos() { return pos_; }
+  const uint8* data() const { return buf_; }
+  int size() const { return size_; }
+  int pos() const { return pos_; }
 
  protected:
   const uint8* buf_;
   int size_;
   int pos_;
 
   template<typename T> bool Read(T* t) WARN_UNUSED_RESULT;
 };
 
 class MEDIA_EXPORT BoxReader : public BufferReader {
@@ skipping 128 matching lines @@
     ++child_itr;
   }
   children_.clear();
   return true;
 }
 
 }  // namespace mp4
 }  // namespace media
 
 #endif  // MEDIA_MP4_BOX_READER_H_