The correct type for the size of a chunk of memory is size_t.

base/shared_memory_nacl.cc

 // 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.
 
 #include "base/shared_memory.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <unistd.h>
 
+#include <limits>
+
 #include "base/logging.h"
 
 namespace base {
 
 SharedMemory::SharedMemory()
     : mapped_file_(-1),
       mapped_size_(0),
       inode_(0),
       memory_(NULL),
       read_only_(false),
@@ skipping 34 matching lines @@
   return SharedMemoryHandle();
 }
 
 // static
 void SharedMemory::CloseHandle(const SharedMemoryHandle& handle) {
   DCHECK_GE(handle.fd, 0);
   if (close(handle.fd) < 0)
     DPLOG(ERROR) << "close";
 }
 
-bool SharedMemory::CreateAndMapAnonymous(uint32 size) {
+bool SharedMemory::CreateAndMapAnonymous(size_t size) {
   // Untrusted code can't create descriptors or handles.
   return false;
 }
 
 bool SharedMemory::Create(const SharedMemoryCreateOptions& options) {
   // Untrusted code can't create descriptors or handles.
   return false;
 }
 
 bool SharedMemory::Delete(const std::string& name) {
   return false;
 }
 
 bool SharedMemory::Open(const std::string& name, bool read_only) {
   return false;
 }
 
-bool SharedMemory::Map(uint32 bytes) {
+bool SharedMemory::Map(size_t bytes) {
   if (mapped_file_ == -1)
     return false;
 
+  if (bytes > static_cast<size_t>(std::numeric_limits<int>::max()))
+    return false;
+
   memory_ = mmap(NULL, bytes, PROT_READ | (read_only_ ? 0 : PROT_WRITE),
                  MAP_SHARED, mapped_file_, 0);
 
   bool mmap_succeeded = memory_ != MAP_FAILED && memory_ != NULL;
   if (mmap_succeeded) {
     mapped_size_ = bytes;
     DCHECK_EQ(0U, reinterpret_cast<uintptr_t>(memory_) &
         (SharedMemory::MAP_MINIMUM_ALIGNMENT - 1));
   } else {
     memory_ = NULL;
@@ skipping 35 matching lines @@
   NOTIMPLEMENTED();
 }
 
 bool SharedMemory::ShareToProcessCommon(ProcessHandle process,
                                         SharedMemoryHandle *new_handle,
                                         bool close_self) {
   return false;
 }
 
 }  // namespace base