Convert CreateCdmBuffer() to use size_t for |capacity|

media/cdm/simple_cdm_buffer.cc

 // Copyright 2015 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.
 
 #include "media/cdm/simple_cdm_buffer.h"
 
+#include <limits>
+
 #include "base/logging.h"
+#include "base/numerics/safe_conversions.h"
 
 namespace media {
 
 // static
-SimpleCdmBuffer* SimpleCdmBuffer::Create(uint32_t capacity) {
+SimpleCdmBuffer* SimpleCdmBuffer::Create(size_t capacity) {
   DCHECK(capacity);
-  return new SimpleCdmBuffer(capacity);
+
+  // cdm::Buffer interface limits capacity to uint32.
+  DCHECK_LE(capacity, std::numeric_limits<uint32_t>::max());
+  return new SimpleCdmBuffer(base::checked_cast<uint32_t>(capacity));
 }
 
 SimpleCdmBuffer::SimpleCdmBuffer(uint32_t capacity)
     : buffer_(capacity), size_(0) {}
 
 SimpleCdmBuffer::~SimpleCdmBuffer() {}
 
 void SimpleCdmBuffer::Destroy() {
   delete this;
 }
 
 uint32_t SimpleCdmBuffer::Capacity() const {
   return buffer_.size();
 }
 
 uint8_t* SimpleCdmBuffer::Data() {
   return buffer_.data();
 }
 
 void SimpleCdmBuffer::SetSize(uint32_t size) {
   DCHECK(size <= Capacity());
   size_ = size > Capacity() ? 0 : size;
 }
 
 uint32_t SimpleCdmBuffer::Size() const {
   return size_;
 }
 
 }  // namespace media