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

base/shared_memory_win.cc

Index: base/shared_memory_win.cc
===================================================================
--- base/shared_memory_win.cc	(revision 175576)
+++ base/shared_memory_win.cc	(working copy)
@@ -70,7 +70,7 @@
   ::CloseHandle(handle);
 }
 
-bool SharedMemory::CreateAndMapAnonymous(uint32 size) {
+bool SharedMemory::CreateAndMapAnonymous(size_t size) {
   return CreateAnonymous(size) && Map(size);
 }
 
@@ -80,6 +80,9 @@
   if (options.size == 0)
     return false;
 
+  if (options.size > static_cast<size_t>(std::numeric_limits<int>::max()))
+    return false;
+
   // NaCl's memory allocator requires 0mod64K alignment and size for
   // shared memory objects.  To allow passing shared memory to NaCl,
   // therefore we round the size actually created to the nearest 64K unit.
@@ -131,10 +134,13 @@
   return false;
 }
 
-bool SharedMemory::Map(uint32 bytes) {
+bool SharedMemory::Map(size_t bytes) {
   if (mapped_file_ == NULL)
     return false;
 
+  if (bytes > static_cast<size_t>(std::numeric_limits<int>::max()))
+    return false;
+
   memory_ = MapViewOfFile(mapped_file_,
       read_only_ ? FILE_MAP_READ : FILE_MAP_ALL_ACCESS, 0, 0, bytes);
   if (memory_ != NULL) {