Added code for renderer to cleanly exit.

base/process_util.cc

Index: base/process_util.cc
diff --git a/base/process_util.cc b/base/process_util.cc
index 9979dfa07b1b06ee9d8aca814da04907200f077d..0d578fb70b5aea99db52dbb4b39a88db1d664e6a 100644
--- a/base/process_util.cc
+++ b/base/process_util.cc
@@ -76,4 +76,19 @@ NamedProcessIterator::NamedProcessIterator(
 NamedProcessIterator::~NamedProcessIterator() {
 }
 
+#if defined(RENDERER_CLEAN_EXIT)
+base::subtle::Atomic32 exit_counter;
+
+extern void clean_exit(int return_value)
+{
+  base::subtle::Atomic32 new_exit_counter;
+  new_exit_counter = base::subtle::
+      Barrier_AtomicIncrement(&exit_counter, (base::subtle::Atomic32)1);
+  if (new_exit_counter == 1)
+    exit(return_value);
+  else
+    pthread_exit(NULL);
+}
+#endif // defined(RENDERER_CLEAN_EXIT)
+
 }  // namespace base