Fix a number of int type issues in dart:io File implementation to avoid implicit conversions that c…

runtime/bin/builtin_natives.cc

Index: runtime/bin/builtin_natives.cc
diff --git a/runtime/bin/builtin_natives.cc b/runtime/bin/builtin_natives.cc
index dcaf06beb880cf20b478d35f5cf3e79fba3a89c6..8fedb2dd2420c797e649fff5563da3c1f6353c44 100644
--- a/runtime/bin/builtin_natives.cc
+++ b/runtime/bin/builtin_natives.cc
@@ -112,5 +112,5 @@ void FUNCTION_NAME(Exit)(Dart_NativeArguments args) {
   // Ignore result if passing invalid argument and just exit 0.
   DartUtils::GetInt64Value(Dart_GetNativeArgument(args, 0), &status);
   Dart_ExitScope();
-  exit(status);
+  exit(static_cast<int>(status));
 }