WebMIDI: Add MIDIOptions dictionary

We have basic support for IDL dictionary so we can use it for
MIDIOptions. Renamed m_sysexEnabled and setSysexEnabled()
because their role have changed.

MIDIOptions is the first IDL dictionary in modules/ so this CL
also contains GYP/GN changes.

Existing tests (LayoutTests/webmidi) should cover this change.

BUG=403150

Review URL: https://codereview.chromium.org/547383004

git-svn-id: svn://svn.chromium.org/blink/trunk@181866 bbb929c8-8fbe-4397-9dbb-9b2b20218538