The patch has been tested on multiple Dolphin versions, including 16.12.3, 17.04 and the latest one: 17.08. Compiles fine, works as expected.
Linux distro used: Arch Linux (64-bit).
The patch file has been applied into the program source code by slightly modifiying an existing PKGBUILD file for dolphin (added patch file as a recognizable source file). The original PKGBUILD file is available here: https://git.archlinux.org/svntogit/packages.git/tree/trunk?h=packages/dolphin
The patch should be considered as a partial implementation. To make the full implementation, see TODO part in Summary field above.
User can disable or enable this feature by following these steps:
1) compile Dolphin from source, apply the patch file
2) install compiled Dolphin package
3) Open Dolphin, and go to Settings -> Configure Dolphin...
4) Open Navigation tab, and enable/disable "Play media files automatically" feature
5) Save your changes