Reland of https://codereview.chromium.org/2034093002 (reverted by
https://codereview.chromium.org/2080153002).

Original commit message:
Implement WASM support on big-endian platforms. WASM has
an implicit requirement that it is running on little-endian
machine. We achieve WASM support on BE by keeping data
in memory in little-endian order, and changing data
endianness before storing to memory and after loading from
memory.

BUG=

Review-Url: https://codereview.chromium.org/2083523002
Cr-Commit-Position: refs/heads/master@{#37373}