This makes sure we use WebAssembly runtime stubs when performing value
coercions in wrapper code that is compiled into {WasmCode}. It hence
removes the last {RelocInfo::CODE_TARGET} references in {WasmCode}.

R=clemensh@chromium.org
BUG=v8:7424

Change-Id: Ic96e541abe98f90796a6506b09ff99557743b6f7
Reviewed-on: https://chromium-review.googlesource.com/1104462
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53846}