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

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/renderer_host/render_sandbox_host_linux.h"
 
 #include <fcntl.h>
 #include <fontconfig/fontconfig.h>
 #include <stdint.h>
 #include <sys/poll.h>
@@ skipping 205 matching lines @@
       return;
     const int result_fd = open(paths_[index]->c_str(), O_RDONLY);
 
     Pickle reply;
     if (result_fd == -1) {
       reply.WriteBool(false);
     } else {
       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)));

[jln (very slow on Chromium), 2013/03/19 10:23:27]

We missed moving this out of DCHECK. And it's arguably the most important. Sorry
again about that.

+    }
   }
 
   void HandleGetFontFamilyForChars(int fd, const Pickle& pickle,
                                    PickleIterator iter,
                                    std::vector<int>& fds) {
     // The other side of this call is
     // chrome/renderer/renderer_sandbox_support_linux.cc
 
     int num_chars;
     if (!pickle.ReadInt(&iter, &num_chars))
@@ skipping 490 matching lines @@
 RenderSandboxHostLinux::~RenderSandboxHostLinux() {
   if (initialized_) {
     if (HANDLE_EINTR(close(renderer_socket_)) < 0)
       PLOG(ERROR) << "close";
     if (HANDLE_EINTR(close(childs_lifeline_fd_)) < 0)
       PLOG(ERROR) << "close";
   }
 }
 
 }  // namespace content