WebGLRenderer: Fix material.wireframeLinewidth. Based on #6778. Should fix #6687.

src/renderers/WebGLRenderer.js

@@ -1033,7 +1033,14 @@ THREE.WebGLRenderer = function ( parameters ) {
 
 	function renderMesh( material, geometry, object, program, updateBuffers ) {
 
-		var mode = material.wireframe === true ? _gl.LINES : _gl.TRIANGLES;
+		var mode = _gl.TRIANGLES;
+
+		if ( material.wireframe === true ) {
+
+			mode = _gl.LINES;
+			state.setLineWidth( material.wireframeLinewidth * pixelRatio );
+
+		}
 
 		var index = geometry.attributes.index;