Revert of Make SandboxIPCProcess a thread.

content/browser/renderer_host/render_sandbox_host_linux.cc

Index: content/browser/renderer_host/render_sandbox_host_linux.cc
diff --git a/content/browser/renderer_host/render_sandbox_host_linux.cc b/content/browser/renderer_host/render_sandbox_host_linux.cc
index a700f9497bb779630ec8c6ebfdf660069fddde62..02b5fee31030376c8bff1435d5c627f69687454b 100644
--- a/content/browser/renderer_host/render_sandbox_host_linux.cc
+++ b/content/browser/renderer_host/render_sandbox_host_linux.cc
@@ -8,12 +8,16 @@
 
 #include "base/memory/singleton.h"
 #include "base/posix/eintr_wrapper.h"
+#include "content/browser/renderer_host/sandbox_ipc_linux.h"
 
 namespace content {
 
 // Runs on the main thread at startup.
 RenderSandboxHostLinux::RenderSandboxHostLinux()
-    : initialized_(false), renderer_socket_(0) {
+    : initialized_(false),
+      renderer_socket_(0),
+      childs_lifeline_fd_(0),
+      pid_(0) {
 }
 
 // static
@@ -44,18 +48,34 @@
   // Instead, it replies on a temporary socket provided by the caller.
   PCHECK(0 == shutdown(browser_socket, SHUT_WR)) << "shutdown";
 
-  ipc_handler_.reset(new SandboxIPCHandler(browser_socket, sandbox_path));
-  ipc_thread_.reset(
-      new base::DelegateSimpleThread(ipc_handler_.get(), "sandbox_ipc_thread"));
-  ipc_thread_->Start();
+  int pipefds[2];
+  CHECK(0 == pipe(pipefds));
+  const int child_lifeline_fd = pipefds[0];
+  childs_lifeline_fd_ = pipefds[1];
+
+  // We need to be monothreaded before we fork().
+#if !defined(THREAD_SANITIZER)
+  DCHECK_EQ(1, base::GetNumberOfThreads(base::GetCurrentProcessHandle()));
+#endif  // !defined(THREAD_SANITIZER)
+  pid_ = fork();
+  if (pid_ == 0) {
+    if (IGNORE_EINTR(close(fds[0])) < 0)
+      DPLOG(ERROR) << "close";
+    if (IGNORE_EINTR(close(pipefds[1])) < 0)
+      DPLOG(ERROR) << "close";
+
+    SandboxIPCProcess handler(child_lifeline_fd, browser_socket, sandbox_path);
+    handler.Run();
+    _exit(0);
+  }
 }
 
 RenderSandboxHostLinux::~RenderSandboxHostLinux() {
   if (initialized_) {
     if (IGNORE_EINTR(close(renderer_socket_)) < 0)
       PLOG(ERROR) << "close";
-
-    ipc_thread_->Join();
+    if (IGNORE_EINTR(close(childs_lifeline_fd_)) < 0)
+      PLOG(ERROR) << "close";
   }
 }