This reverts commit 072d0e3e.

Reason for revert: Performance regressions (https://crbug.com/749041).

Original change's description:
> [wasm] Allow for arbitrarily long error messages
> 
> We currently have a fixed limit of 256 characters for error messages
> generated in the decoder. However, we sometimes embed names in it,
> which makes it easy to generate a crash by using long names (e.g. for
> exports) in invalid wasm modules.
> This CL fixes this by switching to a stream based interface, allowing
> to pass arbitrary objects to be printed. With this interface, we can
> easily limit the length of output later.
> 
> R=​titzer@chromium.org
> 
> Bug: chromium:740023
> Change-Id: I2848c31c63a015157e2a3a9458b54e523060cd69
> Reviewed-on: https://chromium-review.googlesource.com/565282
> Reviewed-by: Ben Titzer <titzer@chromium.org>
> Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#46860}

TBR=titzer@chromium.org,clemensh@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: chromium:740023, chromium:749041
Change-Id: I005a60d55dcf01d350230f8d98f715bab9c43886
Reviewed-on: https://chromium-review.googlesource.com/593807
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47008}