DevTools: Reuse WorkerInspectorProxy in WebEmbeddedWorkerImpl and WebSharedWorkerImpl.

BUG=404355
R=pfeldman, yurys, sergeyv

Review URL: https://codereview.chromium.org/478123003

git-svn-id: svn://svn.chromium.org/blink/trunk@180562 bbb929c8-8fbe-4397-9dbb-9b2b20218538