Fix crashes on debug windows

Fix crashes on debug windows

Committed: https://github.com/dart-lang/sdk/commit/df260e5fe7e0d4e42624e68dc752b5742202764f

[zra, 2016-10-18 16:28:24]

zra@google.com changed reviewers:
+ asiva@google.com, rmacnak@google.com

[zra, 2016-10-18 16:36:48]

TBR

[zra, 2016-10-18 16:37:08]

Description was changed from

==========
Fix crashes on debug windows
==========

to

==========
Fix crashes on debug windows

Committed:
https://github.com/dart-lang/sdk/commit/df260e5fe7e0d4e42624e68dc752b5742202764f
==========

[zra, 2016-10-18 16:37:10]

Committed patchset #3 (id:40001) manually as
df260e5fe7e0d4e42624e68dc752b5742202764f (presubmit successful).

[siva, 2016-10-18 17:32:20]

https://codereview.chromium.org/2426053002/diff/40001/runtime/bin/file.h
File runtime/bin/file.h (right):

https://codereview.chromium.org/2426053002/diff/40001/runtime/bin/file.h#newc...
runtime/bin/file.h:167: // without a scope, they will fail on Windows!
GetType is in this list but it does not call Dart_ScopeAllocate after this CL,
maybe it should be moved out of the list?

I suppose Dart_ScopeAllocate was being used in order to make the
deletion of the allocated wide char string easy. 
It is useful to be able to call these file utility functions without
having to set up a Dart Scope. Could we use the C++ destructor
mechanism to achieve the same?

Something like :
File::Type File::GetType(const char* pathname, bool follow_links) {
  MutiByteToWideChar convert(pathname);
  const wchar_t* name = convert.string();
  ...
  ...
  return result;
}

The destructor of MultiByteToWideChar takes care of deleting the allocated
string.