DevTools: Restore shortcuts in Quick source
DevTools: Restore shortcuts in Quick source

The shortcuts were looking for the SourcesPanel, when only the
SourcesView was present.

Bug: 875434
Change-Id: I6095ccaab4d7ab0c35f98153031e7204f023a30e
Reviewed-on: https://chromium-review.googlesource.com/c/1277988
Reviewed-by: Dmitry Gozman <0ca14b32cbb359a30ac562af27dd84cc2813eacb@chromium.org>
Commit-Queue: Joel Einbinder <bab755abe9fee48fe544272e55f73517d4e4a725@chromium.org>
Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#599322}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 99ba3abbde5c981ca60c0f773b279521df38496d
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