[windows] Make most file_win.cc functions use malloc for string conversions.

runtime/bin/file_macos.cc

Index: runtime/bin/file_macos.cc
diff --git a/runtime/bin/file_macos.cc b/runtime/bin/file_macos.cc
index 0720b6f3437db0d7e218288a3ead4f81d5d9a5de..fe34eb7527445940f92319363126b5b32d9c27f9 100644
--- a/runtime/bin/file_macos.cc
+++ b/runtime/bin/file_macos.cc
@@ -185,7 +185,7 @@ File* File::FileOpenW(const wchar_t* system_name, FileOpenMode mode) {
 }
 
 
-File* File::ScopedOpen(const char* name, FileOpenMode mode) {
+File* File::Open(const char* name, FileOpenMode mode) {
   // Report errors for non-regular files.
   struct stat st;
   if (NO_RETRY_EXPECTED(stat(name, &st)) == 0) {
@@ -223,12 +223,6 @@ File* File::ScopedOpen(const char* name, FileOpenMode mode) {
 }
 
 
-File* File::Open(const char* path, FileOpenMode mode) {
-  // ScopedOpen doesn't actually need a scope.
-  return ScopedOpen(path, mode);
-}
-
-
 File* File::OpenStdio(int fd) {
   return ((fd < 0) || (2 < fd)) ? NULL : new File(new FileHandle(fd));
 }