Check elimination did not mark some dead blocks.

R=danno@chromium.org

Review URL: https://codereview.chromium.org/180483003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19619 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Update README about where the test262 files are downloaded from.

BUG=none
TBR=jkummerow@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/184573003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19620 ce2b1a6d-e550-0410-aec6-3dcde31c8c00