Update tonic for VM roll R=johnmccutchan@google.com Review URL: https://codereview.chromium.org/1822393002 .

diff --git a/dart_vm.cc b/dart_vm.cc
index 023dcf1..a56e682 100644
--- a/dart_vm.cc
+++ b/dart_vm.cc

@@ -19,6 +19,7 @@
   interrupt = nullptr;
   unhandled_exception = nullptr;
   shutdown = nullptr;
+  thread_exit = nullptr;
   file_open = nullptr;
   file_read = nullptr;
   file_write = nullptr;
@@ -48,6 +49,7 @@
                                    config.interrupt,
                                    config.unhandled_exception,
                                    config.shutdown,
+                                   config.thread_exit,
                                    config.file_open,
                                    config.file_read,
                                    config.file_write,

diff --git a/dart_vm.h b/dart_vm.h
index 17e4511..5044c47 100644
--- a/dart_vm.h
+++ b/dart_vm.h

@@ -24,6 +24,7 @@
     Dart_IsolateInterruptCallback interrupt;
     Dart_IsolateUnhandledExceptionCallback unhandled_exception;
     Dart_IsolateShutdownCallback shutdown;
+    Dart_ThreadExitCallback thread_exit;
     Dart_FileOpenCallback file_open;
     Dart_FileReadCallback file_read;
     Dart_FileWriteCallback file_write;