Really remove io support when dart:io is unsupported.

runtime/bin/process.cc

Index: runtime/bin/process.cc
diff --git a/runtime/bin/process.cc b/runtime/bin/process.cc
index 3896505736664f1cfd510583765116adead67699..672b3e352fb7602f95d1b122dcb3346a11b635f1 100644
--- a/runtime/bin/process.cc
+++ b/runtime/bin/process.cc
@@ -2,11 +2,14 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+#if !defined(DART_IO_DISABLED)
+
+#include "bin/process.h"
+
 #include "bin/dartutils.h"
 #include "bin/io_buffer.h"
 #include "bin/log.h"
 #include "bin/platform.h"
-#include "bin/process.h"
 #include "bin/socket.h"
 #include "bin/utils.h"
 
@@ -17,9 +20,6 @@ namespace bin {
 
 static const int kProcessIdNativeField = 0;
 
-int Process::global_exit_code_ = 0;
-Mutex* Process::global_exit_code_mutex_ = new Mutex();
-
 // Extract an array of C strings from a list of Dart strings.
 static char** ExtractCStringList(Dart_Handle strings,
                                  Dart_Handle status_handle,
@@ -367,3 +367,5 @@ void FUNCTION_NAME(StringToSystemEncoding)(Dart_NativeArguments args) {
 
 }  // namespace bin
 }  // namespace dart
+
+#endif  // !defined(DART_IO_DISABLED)