Convert CreateCdmBuffer() to use size_t for |capacity|

media/cdm/simple_cdm_buffer.cc

Index: media/cdm/simple_cdm_buffer.cc
diff --git a/media/cdm/simple_cdm_buffer.cc b/media/cdm/simple_cdm_buffer.cc
index c5f3b8bbf96d0e88d159cb81d49e299a1ad148f8..712c8b7b03b5ac47ed7a8242e2792e1eaac3a987 100644
--- a/media/cdm/simple_cdm_buffer.cc
+++ b/media/cdm/simple_cdm_buffer.cc
@@ -4,14 +4,20 @@
 
 #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)