Rename scopes and context in JSBasedEventListener::handleEvent()

This CL renames some ambiguous name of scope and context in
JSBasedEventListener::handleEvent().

Split from another one:
https://chromium-review.googlesource.com/c/chromium/src/+/1270300

Bug: 872138
Change-Id: I8e772ecdc283fd1585566cf56a52170b777f4608
Reviewed-on: https://chromium-review.googlesource.com/c/1277135
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Commit-Queue: Yuki Yamada <yukiy@google.com>
Cr-Commit-Position: refs/heads/master@{#599114}
1 file changed