MIPS: Implement HChange support for Smis and use it in Load/StoreNameField

Port r14765 (22625125)

BUG=

Review URL: https://codereview.chromium.org/15781006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14782 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
MIPS: Omit smi-check for write-barrier unless tagged.

Port r14767 (40dd85ec)

BUG=

Review URL: https://codereview.chromium.org/15745021

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14783 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
MIPS: Always require exact maps.

Port r14768 (5dec309f)

BUG=

Review URL: https://codereview.chromium.org/15948003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14784 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
MIPS: Improve SeqStringSetChar implementation.

Port r14769 (f0000b20)

BUG=

Review URL: https://codereview.chromium.org/15949002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14785 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
MIPS: Tag length of FixedArrayBase and smi-array[x] as smi representation

Port r14778 (c7fdf61b)

BUG=

Review URL: https://codereview.chromium.org/15927005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14786 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
MIPS: Require smi for keyed store to smi.

Port r14779 (33d24080)

BUG=

Review URL: https://codereview.chromium.org/15889007

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14787 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
MIPS: Fix assert on ARM

Port r14781 (a3491cb7)

BUG=

Review URL: https://codereview.chromium.org/15952002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14788 ce2b1a6d-e550-0410-aec6-3dcde31c8c00