OES_texture_half_float_linear is not implemented on iOS8. Found no corresponding implementation ticket in the tracker.
*** This bug has been marked as a duplicate of bug 133580 ***
iOS 8 Beta 2 still does not have OES_texture_half_float_linear. This functionality is implemented by Chrome and Firefox unprefixed.
Don't worry. https://bugs.webkit.org/show_bug.cgi?id=133580 really fixed it, but it was not included in the iOS8 beta 2 for some reason.
No worries, just wanted record the status.