Show actualy FD for files in Observatory.

runtime/bin/file_win.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
 #if defined(TARGET_OS_WINDOWS)
 
 #include "bin/file.h"
 
 #include <fcntl.h>  // NOLINT
@@ skipping 41 matching lines @@
   } else {
     int err = close(handle_->fd());
     if (err != 0) {
       Log::PrintErr("%s\n", strerror(errno));
     }
   }
   handle_->set_fd(kClosedFd);
 }
 
 
+intptr_t File::GetFD() {
+  return handle_->fd();
+}
+
+
 bool File::IsClosed() {
   return handle_->fd() == kClosedFd;
 }
 
 
 int64_t File::Read(void* buffer, int64_t num_bytes) {
   ASSERT(handle_->fd() >= 0);
   return read(handle_->fd(), buffer, num_bytes);
 }
 
@@ skipping 569 matching lines @@
     return kIdentical;
   } else {
     return kDifferent;
   }
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_WINDOWS)