Do not externalize Dart strings as C strings for "print()".

Do not externalize Dart strings as C strings for "print()".

Dart strings with embedded '\0' characters cannot be faithfully
represented as a C string.

This change adds Dart_StringToBytes to the Dart API.  This function
converts a Dart string to array of UTF-8 code units and returns a
length.  Builtin::PrintString now calls Dart_StringToBytes instead of
Dart_StringToCString and, for I/O, fwrite is called instead of fprintf
with the string format specifier.

BUG=1098
Committed: https://code.google.com/p/dart/source/detail?r=7260

[cshapiro, 2012-05-02 22:10:25]

http://codereview.chromium.org/10306002/diff/1/runtime/vm/dart_api_impl.cc
File runtime/vm/dart_api_impl.cc (right):

http://codereview.chromium.org/10306002/diff/1/runtime/vm/dart_api_impl.cc#ne...
runtime/vm/dart_api_impl.cc:1616: const char** bytes,
This is typed wrong, this should be a uint8_t, I'll fix it before check-in

[siva, 2012-05-02 22:15:48]

lgtm

http://codereview.chromium.org/10306002/diff/1/runtime/vm/dart_api_impl.cc
File runtime/vm/dart_api_impl.cc (right):

http://codereview.chromium.org/10306002/diff/1/runtime/vm/dart_api_impl.cc#ne...
runtime/vm/dart_api_impl.cc:1623: }
if (bytes == NULL) {
  return Api::NewError("%s expects argument 'bytes' to be non-null.",
                         CURRENT_FUNC);
}
if (length == NULL) {
  return Api::NewError("%s expects argument 'length' to be non-null.",
                         CURRENT_FUNC);
}

[cshapiro, 2012-05-02 22:40:59]

http://codereview.chromium.org/10306002/diff/1/runtime/vm/dart_api_impl.cc
File runtime/vm/dart_api_impl.cc (right):

http://codereview.chromium.org/10306002/diff/1/runtime/vm/dart_api_impl.cc#ne...
runtime/vm/dart_api_impl.cc:1623: }
Done.  As an aside, I think we do not do enough argument validation in the Dart
API.  A bug should be filed to clean that up.