Rename LayoutBox to CSSBoxType. Also rename the functions and methods that mention "LayoutBox" to something that makes sense for each specific situation.

This is a merge of http://trac.webkit.org/changeset/165843 by Bem Jones-Bey <bjonesbe@adobe.com>.

BUG=358377

Review URL: https://codereview.chromium.org/220023003

git-svn-id: svn://svn.chromium.org/blink/trunk@170496 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Documents with many lines overallocated pagination info.

There is an object LineFragmentationData that is used for pagination
that is created on demand. That object was created for normal documents
and cost roughly 32 bytes per line, adding up to 3-5 MB on a big text
document (5% of all memory usage).

Testcase: http://norvig.com/big.txt - 3-10 MB RAM savings.

I don't know what I'm doing but this patch prevents the allocation and
saves the memory.

BUG=353993

Review URL: https://codereview.chromium.org/200053007

git-svn-id: svn://svn.chromium.org/blink/trunk@170497 bbb929c8-8fbe-4397-9dbb-9b2b20218538