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

base/shared_memory_posix.cc

Index: base/shared_memory_posix.cc
===================================================================
--- base/shared_memory_posix.cc	(revision 175576)
+++ base/shared_memory_posix.cc	(working copy)
@@ -98,7 +98,7 @@
     DPLOG(ERROR) << "close";
 }
 
-bool SharedMemory::CreateAndMapAnonymous(uint32 size) {
+bool SharedMemory::CreateAndMapAnonymous(size_t size) {
   return CreateAnonymous(size) && Map(size);
 }
 
@@ -113,6 +113,9 @@
   DCHECK_EQ(-1, mapped_file_);
   if (options.size == 0) return false;
 
+  if (options.size > static_cast<size_t>(std::numeric_limits<int>::max()))
+    return false;
+
   // This function theoretically can block on the disk, but realistically
   // the temporary files we create will just go into the buffer cache
   // and be deleted before they ever make it out to disk.
@@ -153,7 +156,7 @@
       file_util::CloseFile(fp);
       return false;
     }
-    const uint32 current_size = stat.st_size;
+    const size_t current_size = stat.st_size;
     if (current_size != options.size) {
       if (HANDLE_EINTR(ftruncate(fileno(fp), options.size)) != 0) {
         file_util::CloseFile(fp);
@@ -216,10 +219,13 @@
 
 #endif  // !defined(OS_ANDROID)
 
-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;
+
 #if defined(OS_ANDROID)
   if (bytes == 0) {
     int ashmem_bytes = ashmem_get_size_region(mapped_file_);