Convert CreateCdmBuffer() to use size_t for |capacity|

media/cdm/cdm_allocator.h

 // Copyright 2016 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_CDM_CDM_ALLOCATOR_H_
 #define MEDIA_CDM_CDM_ALLOCATOR_H_
 
+#include <stddef.h>
 #include <stdint.h>
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "media/base/media_export.h"
 
 namespace cdm {
 class Buffer;
 }
 
 namespace media {
 
 class VideoFrameImpl;
 
 class MEDIA_EXPORT CdmAllocator {
  public:
   virtual ~CdmAllocator();
 
   // Creates a buffer with at least |capacity| bytes. Caller is required to
   // call Destroy() on the returned buffer when it is done with it.
-  virtual cdm::Buffer* CreateCdmBuffer(uint32_t capacity) = 0;
+  virtual cdm::Buffer* CreateCdmBuffer(size_t capacity) = 0;
 
   // Returns a new VideoFrameImpl.
   virtual scoped_ptr<VideoFrameImpl> CreateCdmVideoFrame() = 0;
 
  protected:
   CdmAllocator();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(CdmAllocator);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_CDM_CDM_ALLOCATOR_H_