Merge pull request #7128 from unphased/fix-shadowmap-alpha-confirmed

confirmed fix #7124

src/renderers/webgl/WebGLShadowMap.js

@@ -237,7 +237,7 @@ THREE.WebGLShadowMap = function ( _renderer, _lights, _objects ) {
 		var clearColor = _renderer.getClearColor(),
 		clearAlpha = _renderer.getClearAlpha();
 
-		_gl.clearColor( clearColor.r, clearColor.g, clearColor.b, clearAlpha );
+		_renderer.setClearColor( clearColor, clearAlpha );
 		_state.enable( _gl.BLEND );
 
 		if ( scope.cullFace === THREE.CullFaceFront ) {