Merged r19500 into 3.24 branch.

MIPS: Fix performance regression on sunspider string-unpack-code.

R=jkummerow@chromium.org
BUG=

Review URL: https://codereview.chromium.org/167973007

git-svn-id: https://v8.googlecode.com/svn/branches/3.24@19506 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Disable handle zapping on 3.24 branch in release mode

BUG=318206
R=jkummerow@chromium.org, danno@chromium.org
LOG=y

Review URL: https://codereview.chromium.org/177903002

git-svn-id: https://v8.googlecode.com/svn/branches/3.24@19531 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Merge remote-tracking branch 'upstream/3.24' into 3.24