OrderedHashTable::FindEntry() handlified.

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/260313003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21057 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Wait for sweeper threads in incremental marking step when sweeper threads are done sweeping.

BUG=
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/252123006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21058 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Enable concurrent sweeping.

BUG=
R=jarin@chromium.org

Review URL: https://codereview.chromium.org/253923004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21059 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Merge remote-tracking branch 'upstream/master'