[NaCl SDK} Add EventListener and EventEmitter to support epoll.

native_client_sdk/src/libraries/nacl_io/kernel_handle.cc

Index: native_client_sdk/src/libraries/nacl_io/kernel_handle.cc
diff --git a/native_client_sdk/src/libraries/nacl_io/kernel_handle.cc b/native_client_sdk/src/libraries/nacl_io/kernel_handle.cc
index 12b83a3dcdb23e66c5d1ace1c517c8959a0aa933..d83555822fba1397b709886fdbb8424fa130a492 100644
--- a/native_client_sdk/src/libraries/nacl_io/kernel_handle.cc
+++ b/native_client_sdk/src/libraries/nacl_io/kernel_handle.cc
@@ -21,6 +21,12 @@ KernelHandle::KernelHandle()
 KernelHandle::KernelHandle(const ScopedMount& mnt, const ScopedMountNode& node)
     : mount_(mnt), node_(node), offs_(0) {}
 
+KernelHandle::~KernelHandle() {
+  // Force release order, so that mount persists beyond node
+  node_.reset(NULL);
+  mount_.reset(NULL);
+}
+
 Error KernelHandle::Init(int open_mode) {
   if (open_mode & O_APPEND) {
     size_t node_size;