Revert "Make all references from root shortcuts (except one to GC roots)"

This reverts commit 940418d2e1150499a28cca60b5dd138d351ec652. It resulted in orphan (Document DOM trees) and (Detached DOM trees) nodes.

BUG=chromium:414190
LOG=N
TBR=loislo@chromium.org, yangguo@chromium.org

Review URL: https://codereview.chromium.org/639753007

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24903 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
[turbofan] reduce allocations outside of pipeline

BUG=
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/679793003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24904 ce2b1a6d-e550-0410-aec6-3dcde31c8c00