[cleanup] Remove unneeded externs
[cleanup] Remove unneeded externs

Change-Id: Ife5b0b080093269eecf7c905ba33523d7209f371
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2196400
Commit-Queue: Simon Zünd <38944668e9e2ca98ccd0275b53370f90fa55c113@chromium.org>
Auto-Submit: Peter Marshall <6d0eecbeb7fb9d172f49b4b32481d2466fd89429@chromium.org>
Reviewed-by: Simon Zünd <38944668e9e2ca98ccd0275b53370f90fa55c113@chromium.org>

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