LibIPC: Add missing include and impl on win32

This commit adds a missing include to MessageWindows after header
cleanup. It also implement IPC::File which had its implementation moved
out of the header, without the matching change to the windows
implementation.

Author: R-Goc

Libraries/LibIPC/FileWindows.cpp

@@ -4,6 +4,8 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <LibCore/File.h>
+#include <LibCore/System.h>
 #include <LibIPC/Decoder.h>
 #include <LibIPC/File.h>
 #include <LibIPC/HandleType.h>
@@ -12,6 +14,53 @@
 
 namespace IPC {
 
+File File::adopt_file(NonnullOwnPtr<Core::File> file)
+{
+    return File(file->leak_fd());
+}
+
+File File::adopt_fd(int fd)
+{
+    return File(fd);
+}
+
+ErrorOr<File> File::clone_fd(int fd)
+{
+    int new_fd = TRY(Core::System::dup(fd));
+    return File(new_fd);
+}
+
+File::File(int fd)
+    : m_fd(fd)
+{
+}
+
+File::File(File&& other)
+    : m_fd(exchange(other.m_fd, -1))
+{
+}
+
+File& File::operator=(File&& other)
+{
+    if (this != &other) {
+        m_fd = exchange(other.m_fd, -1);
+    }
+    return *this;
+}
+
+File::~File()
+{
+    if (m_fd != -1)
+        (void)Core::System::close(m_fd);
+}
+
+// FIXME: IPC::Files transferred over the wire always set O_CLOEXEC during decoding. Perhaps we should add an option to
+//        allow the receiver to decide whether to make it O_CLOEXEC or not. Or an attribute in the .ipc file?
+ErrorOr<void> File::clear_close_on_exec()
+{
+    return Core::System::set_close_on_exec(m_fd, false);
+}
+
 template<>
 ErrorOr<File> decode(Decoder& decoder)
 {

Libraries/LibIPC/MessageWindows.cpp

@@ -6,6 +6,7 @@
  */
 
 #include <AK/ByteReader.h>
+#include <LibCore/System.h>
 #include <LibIPC/HandleType.h>
 #include <LibIPC/Message.h>