Re-land Move ScopedFileDescriptor to dbus/file_descriptor.h

ScopedFileDescriptor was initially introduced to facilitate the
management of a 'lifeline' FD used when asking permission_broker to
open a port in the device's firewall on CrOS.  It's actually a scoped
wrapper around DBus::FileDescriptor, not a platform file descriptor. I
would like to use it to facilitate some other similar functionality in
which I create a pipe and pass one end over DBus, so it seems like a
good idea to move ScopedFileDescriptor into the dbus library directly.

This reverts commit ee9dc849ffa2df2820381c31d5ba8200774d287a.

BUG=chromium:481340
TEST=FirewallHole unit tests still pass
TBR=stevenjb, reillyg, keybuk

Review URL: https://codereview.chromium.org/1108083003

Cr-Commit-Position: refs/heads/master@{#327141}

2 files changed, 19 insertions, 0 deletions

diff --git a/dbus/file_descriptor.cc b/dbus/file_descriptor.cc
index d2d6a31..e607fc0 100644
--- a/dbus/file_descriptor.cc
+++ b/dbus/file_descriptor.cc
@@ -2,12 +2,21 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "base/bind.h"
 #include "base/files/file.h"
+#include "base/location.h"
 #include "base/logging.h"
+#include "base/threading/worker_pool.h"
 #include "dbus/file_descriptor.h"
 
 namespace dbus {
 
+void CHROME_DBUS_EXPORT FileDescriptor::Deleter::operator()(
+    FileDescriptor* fd) {
+  base::WorkerPool::PostTask(
+      FROM_HERE, base::Bind(&base::DeletePointer<FileDescriptor>, fd), false);
+}
+
 FileDescriptor::~FileDescriptor() {
   if (owner_)
     base::File auto_closer(value_);
diff --git a/dbus/file_descriptor.h b/dbus/file_descriptor.h
index 19e0b1a..a01ee6e 100644
--- a/dbus/file_descriptor.h
+++ b/dbus/file_descriptor.h
@@ -6,6 +6,7 @@
 #define DBUS_FILE_DESCRIPTOR_H_
 
 #include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
 #include "dbus/dbus_export.h"
 
 namespace dbus {
@@ -33,6 +34,12 @@ namespace dbus {
 // with i/o restrictions.
 class CHROME_DBUS_EXPORT FileDescriptor {
  public:
+  // This provides a simple way to pass around file descriptors since they must
+  // be closed on a thread that is allowed to perform I/O.
+  struct Deleter {
+    void CHROME_DBUS_EXPORT operator()(FileDescriptor* fd);
+  };
+
   // Permits initialization without a value for passing to
   // dbus::MessageReader::PopFileDescriptor to fill in and from int values.
   FileDescriptor() : value_(-1), owner_(false), valid_(false) {}
@@ -70,6 +77,9 @@ class CHROME_DBUS_EXPORT FileDescriptor {
   DISALLOW_COPY_AND_ASSIGN(FileDescriptor);
 };
 
+using ScopedFileDescriptor =
+    scoped_ptr<FileDescriptor, FileDescriptor::Deleter>;
+
 }  // namespace dbus
 
 #endif  // DBUS_FILE_DESCRIPTOR_H_