Add Process.runSync for running processe synchronously.

runtime/bin/io_buffer.h

Index: runtime/bin/io_buffer.h
diff --git a/runtime/bin/io_buffer.h b/runtime/bin/io_buffer.h
index 1dfcc00252b594ab00691eb4bcc1ea9bf4c8725c..79d55643b06f3fc16e82576d6eec1303024eaca5 100644
--- a/runtime/bin/io_buffer.h
+++ b/runtime/bin/io_buffer.h
@@ -19,6 +19,11 @@ class IOBuffer {
   // an external byte array.
   static Dart_Handle Allocate(intptr_t size, uint8_t **buffer);
 
+  // Create an IO buffer backed by an external byte array. The buffer must
+  // have been allocated using the new operator and it will be freed using
+  // delete.
+  static Dart_Handle Create(uint8_t *buffer, intptr_t size);
+
   // Allocate IO buffer storage.
   static uint8_t* Allocate(intptr_t size);