Added SharedMemory::MapFrom.

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>
@@ skipping 66 matching lines @@
 }
 
 bool SharedMemory::Delete(const std::string& name) {
   return false;
 }
 
 bool SharedMemory::Open(const std::string& name, bool read_only) {
   return false;
 }
 
-bool SharedMemory::Map(size_t bytes) {
+bool SharedMemory::MapAt(off_t offset, 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);
+                 MAP_SHARED, mapped_file_, offset);
 
   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 44 matching lines @@
 
   new_handle->fd = new_fd;
   new_handle->auto_close = true;
 
   if (close_self)
     Close();
   return true;
 }
 
 }  // namespace base