Force GC before executing unbox double arrays test to avoid timeouts.

BUG=

Review URL: https://codereview.chromium.org/15292002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14743 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Use explicit type feedback clearing in some tests.

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/15711004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14744 ce2b1a6d-e550-0410-aec6-3dcde31c8c00