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;