WebKit2.UserContentInjectedFrames

Specifies in which frames user style sheets are to be inserted in.

Since 2.6

UserContentInjectedFrames.ALL_FRAMES: Insert the user style sheet in all the frames loaded by the web view, including nested frames. This is the default.
UserContentInjectedFrames.TOP_FRAME: Insert the user style sheet *only* in the top-level frame loaded by the web view, and *not* in the nested frames.