MIPS: Use TempDoubleRegister.

Port r21517 (53d6507)

BUG=
R=plind44@gmail.com

Review URL: https://codereview.chromium.org/305563002

Patch from Balazs Kilvady <kilvadyb@homejinni.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21537 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Fix check for empty type

R=mstarzinger@chromium.org
BUG=

Review URL: https://codereview.chromium.org/307453005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21538 ce2b1a6d-e550-0410-aec6-3dcde31c8c00