Port 4f3e168c

Original Commit Message:

    This CL adds general lazy compilation support to WebAssembly, according
    to the design described in the design doc (see referenced bug).

    It's not used currently, but I tested locally that all tests succeed if
    I enable it by default.

    With a later CL, we will enable lazy compilation by default for
    validate-asm: https://chromium-review.googlesource.com/451318

R=clemensh@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=v8:5991
LOG=N

Review-Url: https://codereview.chromium.org/2761773004
Cr-Commit-Position: refs/heads/master@{#43954}