Add JSBasedEventListener::GetSourceLocation()

This CL adds JSBasedEventListener::GetSourceLocation().
JSEventHandlerForContentAttribute can provide its SourceLocation even
if it cannot get compiled, so it overrides this method.

Bug: 872138
Change-Id: I8d575f3e847d37b7eb202833971fb610c589dd8f
Reviewed-on: https://chromium-review.googlesource.com/c/1253317
Commit-Queue: Yuki Yamada <yukiy@google.com>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Hayato Ito <hayato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#597837}
5 files changed