Port 5fecd146

Original Commit Message:

    This adds support for unaligned load/store access to the DataView
    backing store and uses byteswap operations to fix up the endianess
    when necessary. This changes the Word32ReverseBytes operator to be
    a required operator and adds the missing support on the Intel and
    ARM platforms (on 64-bit platforms the Word64ReverseBytes operator
    is also mandatory now).

    This further improves the performance on the dataviewperf.js test
    mentioned in the tracking bug by up to 40%, and at the same time
    reduces the code complexity in the EffectControlLinearizer.

R=bmeurer@chromium.org, joransiu@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=
LOG=N

Change-Id: Ia9aad21713a2ad76ce3ef2b816fc20e9a27fe4c9
Reviewed-on: https://chromium-review.googlesource.com/1174936Reviewed-by: John Barboza <jbarboza@ca.ibm.com>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#55132}