Revert "Reland [Object.observe] Don't force normalization of elements for observed objects"

TBR=danno
BUG=

Review URL: https://codereview.chromium.org/67233002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17608 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
MIPS: Reland 17588: Add signed/unsigned 8-bit and 16-bit Representations to Crankshaft.

Port r17606 (bc5ef55)

BUG=
R=plind44@gmail.com

Review URL: https://codereview.chromium.org/66163007

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

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17609 ce2b1a6d-e550-0410-aec6-3dcde31c8c00