DevTools: resume targets after trace loaded
DevTools: resume targets after trace loaded

When we measure the performance of a Node.js app, we need a clear signal
when frontend gets all necessary tracing data, and we can disconnect
from process.
We can move resumeTargets call later and use it as such signal.

R=52e51c43e283548b762e3c9dd9a4600768db9fb4@chromium.org

Bug: none
Change-Id: I4908dd59e1f9d5adb1d473bc0a06d0bfc488c23e
Reviewed-on: https://chromium-review.googlesource.com/1220397
Reviewed-by: Alexei Filippov <52e51c43e283548b762e3c9dd9a4600768db9fb4@chromium.org>
Commit-Queue: Aleksey Kozyatinskiy <562acbea96970f508ad9f5cc9fc7c62d82dd3ef8@chromium.org>
Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#590840}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: e3c0571b911459aa128bc0c2bc6bcde378cae359
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