Revert of [DevTools] Implement DevToolsManager::Observer which notifies about target updates. (patchset #5 id:80001 of https://codereview.chromium.org/
577923002/)
Reason for revert:
Breaks asan bot.
http://build.chromium.org/p/chromium.memory/builders/Linux%20ASan%20LSan%20Tests%20%282%29/builds/7924
Original issue's description:
> [DevTools] Implement DevToolsManager::Observer which notifies about target updates.
>
> BUG=398049
>
> Committed: https://crrev.com/
509c17cf55a12b49b017245f6d0cff558f312637
> Cr-Commit-Position: refs/heads/master@{#296921}
TBR=pfeldman@chromium.org,vkuzkokov@chromium.org,jam@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=398049
Review URL: https://codereview.chromium.org/
591313006
Cr-Commit-Position: refs/heads/master@{#296944}