You don't need a plugin or the Google API, you can add it as a XYZ tile layer.
Streets
googleStreets = L.tileLayer('http://{s}.google.com/vt/lyrs=m&x={x}&y={y}&z={z}',{ maxZoom: 20, subdomains:['mt0','mt1','mt2','mt3'] });
Hybrid:
googleHybrid = L.tileLayer('http://{s}.google.com/vt/lyrs=s,h&x={x}&y={y}&z={z}',{ maxZoom: 20, subdomains:['mt0','mt1','mt2','mt3'] });
Satellite:
googleSat = L.tileLayer('http://{s}.google.com/vt/lyrs=s&x={x}&y={y}&z={z}',{ maxZoom: 20, subdomains:['mt0','mt1','mt2','mt3'] });
Terrain
googleTerrain = L.tileLayer('http://{s}.google.com/vt/lyrs=p&x={x}&y={y}&z={z}',{ maxZoom: 20, subdomains:['mt0','mt1','mt2','mt3'] });
Note the difference in the "lyrs" parameter in the URL: Hybrid: s,h; Satellite: s; Streets: m; Terrain: p;