DevTools: Polyfill Custom Elements V0 for old frontends
DevTools: Polyfill Custom Elements V0 for old frontends

Bug: 685385
Change-Id: I1adae3ac86a2af361b1253f7e723aa86a7ce397e
Reviewed-on: https://chromium-review.googlesource.com/c/1371086
Reviewed-by: Dmitry Gozman <0ca14b32cbb359a30ac562af27dd84cc2813eacb@chromium.org>
Commit-Queue: Joel Einbinder <bab755abe9fee48fe544272e55f73517d4e4a725@chromium.org>
Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#615780}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 64e9bfb30b51952e956210ce1c60a6b69e2b405f
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