Remove window.postMessage(message, transferables, targetOrigin) legacy overload

Intent to Deprecate and Remove:
https://groups.google.com/a/chromium.org/d/msg/blink-dev/h4ooaB_Y9JE/nh7vXshGBwAJ

BUG=425896,640825
R=sigbjornf@opera.com,haraken@chromium.org
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2295863002
Cr-Commit-Position: refs/heads/master@{#417066}
(cherry picked from commit 77a58a92f789f4fd7099b2b4ff87cad27eea3067)

Review URL: https://codereview.chromium.org/2336133002 .

Cr-Commit-Position: refs/branch-heads/2840@{#322}
Cr-Branched-From: 1ae106dbab4bddd85132d5b75c670794311f4c57-refs/heads/master@{#414607}
8 files changed