Fix various places in the code found by improved GCMole.

Review URL: http://codereview.chromium.org/6973063

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7895 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

GCMole is a simple static analysis tool that searches for GC-usafe evaluation order dependent callsites.

Review URL: http://codereview.chromium.org/6812002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7540 ce2b1a6d-e550-0410-aec6-3dcde31c8c00