Avoid needless int64_t to intptr_t conversion in eventhandler.

runtime/bin/eventhandler_win.cc

Index: runtime/bin/eventhandler_win.cc
diff --git a/runtime/bin/eventhandler_win.cc b/runtime/bin/eventhandler_win.cc
index 4917a089152f7cf9ac8f3424d6fa0a3e0d287f27..2d4343b47baeebfcb8320a5895e3267af46d5854 100644
--- a/runtime/bin/eventhandler_win.cc
+++ b/runtime/bin/eventhandler_win.cc
@@ -846,7 +846,7 @@ DWORD EventHandlerImplementation::GetTimeout() {
 
 void EventHandlerImplementation::SendData(intptr_t id,
                                           Dart_Port dart_port,
-                                          intptr_t data) {
+                                          int64_t data) {
   InterruptMessage* msg = new InterruptMessage;
   msg->id = id;
   msg->dart_port = dart_port;