Editor: Refactor encoding settings for background.

editor/js/Viewport.js

@@ -498,6 +498,12 @@ var Viewport = function ( editor ) {
 
 		}
 
+		if ( scene.background !== null && ( scene.background.isTexture || scene.background.isCubeTexture ) ) {
+
+			scene.background.encoding = THREE.sRGBEncoding;
+
+		}
+
 		render();
 
 	} );

editor/js/libs/ui.three.js

@@ -246,7 +246,6 @@ var UICubeTexture = function () {
 		if ( images.length === 6 ) {
 
 			var cubeTexture = new THREE.CubeTexture( images );
-			cubeTexture.encoding = THREE.sRGBEncoding;
 			cubeTexture.needsUpdate = true;
 
 			scope.cubeTexture = cubeTexture;