Advertise a minimum alignment for SharedMemory::Map().

base/shared_memory_posix.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 222 matching lines @@
     // transport_dib_android.cc. We should use ashmem_get_size_region()
     // in transport_dib_android.cc.
     created_size_ = bytes;
   }
 #endif
 
   memory_ = mmap(NULL, bytes, PROT_READ | (read_only_ ? 0 : PROT_WRITE),
                  MAP_SHARED, mapped_file_, 0);
 
   bool mmap_succeeded = memory_ != (void*)-1 && memory_ != NULL;
-  if (mmap_succeeded)
+  if (mmap_succeeded) {
     mapped_size_ = bytes;
-  else
+    DCHECK_EQ(0U, reinterpret_cast<uintptr_t>(memory_) &
+        (SharedMemory::MAP_MINIMUM_ALIGNMENT - 1));
+  } else {
     memory_ = NULL;
+  }
 
   return mmap_succeeded;
 }
 
 bool SharedMemory::Unmap() {
   if (memory_ == NULL)
     return false;
 
   munmap(memory_, mapped_size_);
   memory_ = NULL;
@@ skipping 110 matching lines @@
   new_handle->fd = new_fd;
   new_handle->auto_close = true;
 
   if (close_self)
     Close();
 
   return true;
 }
 
 }  // namespace base