Move LiveNodeListBase class to its own header

Move LiveNodeListBase class to its own header

Move LiveNodeListBase class to its own header instead of having it in the
LiveNodeList header. HTMLCollection also inherits from LiveNodeListBase
and is not interested in the LiveNodeList class.

There is still LiveNodeListBase code in HTMLCollection.cpp, this will be
moved in a follow-up patch.

R=esprehn, adamk

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=167821

[Inactive, 2014-02-25 16:37:48]

This is the easy part. The tougher one will be extracting the LiveNodeListBase
code from HTMLCollection.cpp later.

[adamk, 2014-02-25 18:27:56]

lgtm

[commit-bot: I haz the power, 2014-02-25 18:29:59]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/ch.dumez@samsung.com/177213010/1

[commit-bot: I haz the power, 2014-02-25 20:20:15]

Change committed as 167821