PNaCl translation cache: Don't close null nexe fd on renderer shutdown

Check the FD before attempting to close it, but continue to clear out the
pending translation requests.

Bug: 825971
Change-Id: Ia7f452586b6036b19859ed61d8cdbd74334aa0d4
Reviewed-on: https://chromium-review.googlesource.com/981324Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Derek Schuff <dschuff@chromium.org>
Cr-Commit-Position: refs/heads/master@{#545939}

components/nacl/browser/pnacl_host.cc

@@ -566,9 +566,11 @@ void PnaclHost::RendererClosing(int render_process_id) {
     PendingTranslationMap::iterator to_erase(it++);
     if (to_erase->first.first == render_process_id) {
       // Clean up the open files.
-      std::unique_ptr<base::File> file(to_erase->second.nexe_fd);
-      to_erase->second.nexe_fd = NULL;
-      CloseBaseFile(std::move(*file.get()));
+      if (to_erase->second.nexe_fd) {
+        std::unique_ptr<base::File> file(to_erase->second.nexe_fd);
+        to_erase->second.nexe_fd = NULL;
+        CloseBaseFile(std::move(*file.get()));
+      }
       std::string key(to_erase->second.cache_key);
       bool may_be_cached = TranslationMayBeCached(to_erase);
       pending_translations_.erase(to_erase);