Check for is_javascript in Debug::AllFramesOnStackAreBlackboxed,
instead of assuming all frames are javascript frames.

Fix is thanks to dgozman: https://crbug.com/896093#c3

Bug: chromium:896093
Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: I6b735d904c3fd036d4589d65f10673b81b8f326c
Reviewed-on: https://chromium-review.googlesource.com/c/1295552Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Commit-Queue: Kai Ninomiya <kainino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56970}