Eclipse 4.6 has automatic support for substituting icons with high resolution versions on high resolution monitors. This relies on the convention (borrowed from Apple's platforms) to append "@2x" to the file name, before the extension, for the HiDPI versions. To complement this, if there are no high resolution icons, the low resolution icons are now properly scaled on Windows and Linux, mimicking the default behavior on macOS.
This means that we should now be able to seamlessly add HiDPI versions of our icons without using explicit HiDPI API:s, which were introduced in Eclipse 4.5. Now, it is somewhat unclear as to which extent Eclipse itself have supplied HiDPI icons, but they can be spotted in some places in Eclipse 4.6 (like the Help menu).