Add flow graph printing into a .cfg file with flag --print-flow-graph-file.

vm/os_linux.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // 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.
 
 #include "vm/os.h"
 
 #include <errno.h>
 #include <limits.h>
 #include <time.h>
 #include <sys/resource.h>
@@ skipping 159 matching lines @@
 
 
 void OS::Print(const char* format, ...) {
   va_list args;
   va_start(args, format);
   VFPrint(stdout, format, args);
   va_end(args);
 }
 
 
+void OS::FPrint(FILE* stream, const char* format, ...) {
+  va_list args;
+  va_start(args, format);
+  VFPrint(stream, format, args);
+  va_end(args);
+}
+
+
 void OS::VFPrint(FILE* stream, const char* format, va_list args) {
   vfprintf(stream, format, args);
   fflush(stream);
 }
 
 
 int OS::SNPrint(char* str, size_t size, const char* format, ...) {
   va_list args;
   va_start(args, format);
   int retval = VSNPrint(str, size, format, args);
   va_end(args);
   return retval;
 }
 
 
 int OS::VSNPrint(char* str, size_t size, const char* format, va_list args) {
   return vsnprintf(str, size, format, args);
 }
 
 
 void OS::PrintErr(const char* format, ...) {
   va_list args;
   va_start(args, format);
   VFPrint(stderr, format, args);
   va_end(args);
 }
 
 
+FILE* OS::FOpen(const char* path, const char* mode) {
+  FILE* file = fopen(path, mode);
+  if (file == NULL) return NULL;
+  return file;
+}
+
+
 void OS::InitOnce() {
   // TODO(5411554): For now we check that initonce is called only once,
   // Once there is more formal mechanism to call InitOnce we can move
   // this check there.
   static bool init_once_called = false;
   ASSERT(init_once_called == false);
   init_once_called = true;
 }
 
 
 void OS::Shutdown() {
 }
 
 
 void OS::Abort() {
   abort();
 }
 
 
 void OS::Exit(int code) {
   exit(code);
 }
 
 }  // namespace dart