vo_gpu_next: implement VOCTRL_EXTERNAL_RESIZE

This is only needed on Android and supposed to handle a context
resize without reconfiguring the image parameters. reconfig()
already does exactly this so plug it in there.

video/out/vo.h

@@ -122,7 +122,7 @@ enum mp_voctrl {
     VOCTRL_GET_HIDPI_SCALE,             // double*
     VOCTRL_GET_DISPLAY_RES,             // int[2]
 
-    /* private to vo_gpu */
+    /* private to vo_gpu and vo_gpu_next */
     VOCTRL_EXTERNAL_RESIZE,
 };
 

video/out/vo_gpu_next.c

@@ -1040,6 +1040,10 @@ static int control(struct vo *vo, uint32_t request, void *data)
     case VOCTRL_SCREENSHOT:
         video_screenshot(vo, data);
         return true;
+
+    case VOCTRL_EXTERNAL_RESIZE:
+        reconfig(vo, NULL);
+        return true;
     }
 
     int events = 0;