MIPS: Don't explicitly pass requested representations to constants; implement ConstantS

Port r14874 (e93cc94e)

BUG=

Review URL: https://codereview.chromium.org/15731008

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14890 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
MIPS: Update ASSERT on arm to support SmiOrTagged in ClampToUint8

Port r14881 (0b784159)

BUG=

Review URL: https://codereview.chromium.org/15769005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14891 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
MIPS: Fix AccessArgumentsAt on ARM. Use register for index.

Port r14885 (63dd99b)

BUG=

Review URL: https://codereview.chromium.org/16215002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14892 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
MIPS: Convert ToBooleanStub to a HydrogenStub. Currently just using the existing HBranch instruction, which is still fully implemented in Lithium. Will refactor HBranch in a next CL.

Port r14886 (068e9135)

BUG=

Review URL: https://codereview.chromium.org/15664008

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14893 ce2b1a6d-e550-0410-aec6-3dcde31c8c00