Version 3.26.31.4 (merged r21509, r21858, r21525)

Avoid HeapObject check in HStoreNamedField.

Add unit test for regression in GVN caused by field type tracking.

MIPS: Avoid HeapObject check in HStoreNamedField.

BUG=v8:3347
LOG=N
R=ishell@chromium.org

Review URL: https://codereview.chromium.org/334243002

git-svn-id: https://v8.googlecode.com/svn/branches/3.26@21860 ce2b1a6d-e550-0410-aec6-3dcde31c8c00