Fixes leak of native File objects.

runtime/bin/file_macos.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 "platform/globals.h"
 #if defined(TARGET_OS_MACOS)
 
 #include "bin/file.h"
 
 #include <copyfile.h>  // NOLINT
@@ skipping 22 matching lines @@
   void set_fd(int fd) { fd_ = fd; }
 
  private:
   int fd_;
 
   DISALLOW_COPY_AND_ASSIGN(FileHandle);
 };
 
 
 File::~File() {
-  Close();
+  if (!IsClosed()) {
+    Close();
+  }
   delete handle_;
 }
 
 
 void File::Close() {
   ASSERT(handle_->fd() >= 0);
   if (handle_->fd() == STDOUT_FILENO) {
     // If stdout, redirect fd to /dev/null.
     intptr_t null_fd = TEMP_FAILURE_RETRY(open("/dev/null", O_WRONLY));
     ASSERT(null_fd >= 0);
@@ skipping 138 matching lines @@
 }
 
 
 File* File::Open(const char* path, FileOpenMode mode) {
   // ScopedOpen doesn't actually need a scope.
   return ScopedOpen(path, mode);
 }
 
 
 File* File::OpenStdio(int fd) {
-  if ((fd < 0) || (2 < fd)) {
-    return NULL;
-  }
-  return new File(new FileHandle(fd));
+  return ((fd < 0) || (2 < fd)) ? NULL : new File(new FileHandle(fd));
 }
 
 
 bool File::Exists(const char* name) {
   struct stat st;
   if (NO_RETRY_EXPECTED(stat(name, &st)) == 0) {
     return S_ISREG(st.st_mode);
   } else {
     return false;
   }
@@ skipping 246 matching lines @@
   return ((file_1_info.st_ino == file_2_info.st_ino) &&
           (file_1_info.st_dev == file_2_info.st_dev)) ?
       File::kIdentical :
       File::kDifferent;
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_MACOS)