Linux: tear down Zygote at browser shutdown.

content/browser/browser_main_loop.cc

Index: content/browser/browser_main_loop.cc
diff --git a/content/browser/browser_main_loop.cc b/content/browser/browser_main_loop.cc
index 23d29367aedf0aed0db280417be3e5b1d3850f2e..cc8e6c562f89a52d22fbb499dbd434715fa6fc41 100644
--- a/content/browser/browser_main_loop.cc
+++ b/content/browser/browser_main_loop.cc
@@ -783,6 +783,10 @@ void BrowserMainLoop::ShutdownThreadsAndCleanUp() {
   }
 #endif
 
+#if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_ANDROID)
+  ZygoteHostImpl::GetInstance()->TearDownAfterLastChild();
+#endif  // defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_ANDROID)
+
   // The device monitors are using |system_monitor_| as dependency, so delete
   // them before |system_monitor_| goes away.
   // On Mac and windows, the monitor needs to be destroyed on the same thread