Revert 22380 to investigate windows build break.

runtime/vm/dart.cc

Index: runtime/vm/dart.cc
===================================================================
--- runtime/vm/dart.cc	(revision 22381)
+++ runtime/vm/dart.cc	(working copy)
@@ -80,14 +80,13 @@
                            Dart_IsolateUnhandledExceptionCallback unhandled,
                            Dart_IsolateShutdownCallback shutdown,
                            Dart_FileOpenCallback file_open,
-                           Dart_FileReadCallback file_read,
                            Dart_FileWriteCallback file_write,
                            Dart_FileCloseCallback file_close) {
   // TODO(iposva): Fix race condition here.
   if (vm_isolate_ != NULL || !Flags::Initialized()) {
     return "VM already initialized.";
   }
-  Isolate::SetFileCallbacks(file_open, file_read, file_write, file_close);
+  Isolate::SetFileCallbacks(file_open, file_write, file_close);
   OS::InitOnce();
   VirtualMemory::InitOnce();
   Isolate::InitOnce();