Convert CreateCdmBuffer() to use size_t for |capacity|

media/mojo/services/mojo_cdm_allocator_unittest.cc

Index: media/mojo/services/mojo_cdm_allocator_unittest.cc
diff --git a/media/mojo/services/mojo_cdm_allocator_unittest.cc b/media/mojo/services/mojo_cdm_allocator_unittest.cc
index 6a3d8d10123c065501c4bd4ea712e1af01eabc7c..47fa111476a7a91067e3a297979f20c76b96b4bf 100644
--- a/media/mojo/services/mojo_cdm_allocator_unittest.cc
+++ b/media/mojo/services/mojo_cdm_allocator_unittest.cc
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <stddef.h>
 #include <stdint.h>
 
 #include <cstring>
@@ -22,7 +23,7 @@ class MojoCdmAllocatorTest : public testing::Test {
   ~MojoCdmAllocatorTest() override {}
 
  protected:
-  cdm::Buffer* CreateCdmBuffer(uint32_t capacity) {
+  cdm::Buffer* CreateCdmBuffer(size_t capacity) {
     return allocator_.CreateCdmBuffer(capacity);
   }