Removed unused headers

This CL removes unused includes regarding to
blink::V8AbstractEventHandler and blink::V8EventListenerOrEventHandler.

Bug: 872138
Change-Id: I0fec7187851165e36f1bef0508cecced1f1202b7
Reviewed-on: https://chromium-review.googlesource.com/1206751
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Commit-Queue: Yuki Yamada <yukiy@google.com>
Cr-Commit-Position: refs/heads/master@{#589093}
5 files changed