Move exception handling into ErrorEvent

This CL moves the methods that is for storing/loading exceptions
into blink::ErrorEvent. These methods were in blink::V8ErrorHandler,
but they are not related to it directly.

Bug: 872138
Change-Id: I9e60a9b58e786309d9410d47849b53233a47bd27
Reviewed-on: https://chromium-review.googlesource.com/1212248
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Commit-Queue: Yuki Yamada <yukiy@google.com>
Cr-Commit-Position: refs/heads/master@{#589878}
8 files changed