mmap the opened file descriptor in the renderer process, close the fd in the browser process.

content/browser/renderer_host/render_sandbox_host_linux.cc

Index: content/browser/renderer_host/render_sandbox_host_linux.cc
===================================================================
--- content/browser/renderer_host/render_sandbox_host_linux.cc	(revision 188729)
+++ content/browser/renderer_host/render_sandbox_host_linux.cc	(working copy)
@@ -223,7 +223,13 @@
       reply.WriteBool(true);
     }
 
+    // The receiver will have its own access to the file, so we will close it
+    // after this send.
     SendRendererReply(fds, reply, result_fd);
+
+    if (result_fd >= 0) {
+      DCHECK(!HANDLE_EINTR(close(result_fd)));
+    }
   }
 
   void HandleGetFontFamilyForChars(int fd, const Pickle& pickle,