Merged r17425, r17428 into trunk branch.

Temporarily allow HistogramTimerScopes to be nested

ia32: Fix comparisons of two constant double operands when exactly one of them is in new space.

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/50463003

git-svn-id: https://v8.googlecode.com/svn/trunk@17429 ce2b1a6d-e550-0410-aec6-3dcde31c8c00