StereoEffect: Handle clear differently. (#29125)

* StereoEffect: Handle clear differently.

* E2E: Update screenshots.

examples/jsm/effects/StereoEffect.js

@@ -31,9 +31,12 @@ class StereoEffect {
 
 			_stereo.update( camera );
 
+			const currentAutoClear = renderer.autoClear;
 			renderer.getSize( size );
 
-			if ( renderer.autoClear ) renderer.clear();
+			renderer.autoClear = false;
+			renderer.clear();
+
 			renderer.setScissorTest( true );
 
 			renderer.setScissor( 0, 0, size.width / 2, size.height );
@@ -46,6 +49,8 @@ class StereoEffect {
 
 			renderer.setScissorTest( false );
 
+			renderer.autoClear = currentAutoClear;
+
 		};
 
 	}