CheckPrototypes uses weak cells to embed maps.

BUG=v8:3629
LOG=N

Review URL: https://codereview.chromium.org/770373002

Cr-Commit-Position: refs/heads/master@{#25634}
MIPS: Fix ambiguous double constant loading after adding checked load/store operators.

The V8_INFINITY macro expands to constant expression of type float.

TEST=mjsunit/constant-folding-2
BUG=
R=balazs.kilvady@imgtec.com

Review URL: https://codereview.chromium.org/779433003

Cr-Commit-Position: refs/heads/master@{#25635}
MIPS: Improve pushing arguments on stack.

TEST=
BUG=
R=paul.lind@imgtec.com

Review URL: https://codereview.chromium.org/769283002

Cr-Commit-Position: refs/heads/master@{#25636}