[DevTools] instrument load and error events with async stacks

Some frameworks actively use load and error events for dynamic script
loading. This async stacks can be super usefull in initiator stack in
network panel.

R=dgozman@chromium.org
TBR=pfeldman@chromium.org

Bug: chromium:550453
Change-Id: Idb2a31364421e17e456cfeb0bf9b4a299f0d50b7
Reviewed-on: https://chromium-review.googlesource.com/852854
Reviewed-by: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#527489}
12 files changed