I think it very much depends on the context, though. I would argue that the icons in this screenshot are very easy to understand the meaning of.

The top left is a close icon, then going from right to left of the group in the top right, I'd say that's a download/save icon, then delete, then Google's commonly used vertical ellipsis that brings up more options.

I've never even seen this Material Design app before and have never touched an Android L phone either, but I think I'd be confident knowing what the icons did if I used it.

The silly little geometric shapes at the bottom, which I believe are system-level controls... I have no idea what those mean.