Enable shared memory handle sharing in NaCl.

The destructor for base::SharedMemory closes its handle on destruction.
To keep a shared memory region alive after using it, we need to
duplicate the handle. This uses dup(), which is available in native
client.

BUG=


Review URL: https://chromiumcodereview.appspot.com/11817020

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@176133 0039d316-1c4b-4281-b951-d872f2087c98

base/shared_memory_nacl.cc

@@ -142,7 +142,18 @@ void SharedMemory::Unlock() {
 bool SharedMemory::ShareToProcessCommon(ProcessHandle process,
                                         SharedMemoryHandle *new_handle,
                                         bool close_self) {
-  return false;
+  const int new_fd = dup(mapped_file_);
+  if (new_fd < 0) {
+    DPLOG(ERROR) << "dup() failed.";
+    return false;
+  }
+
+  new_handle->fd = new_fd;
+  new_handle->auto_close = true;
+
+  if (close_self)
+    Close();
+  return true;
 }
 
 }  // namespace base