Revert ScopedTracker changes to  measure the jank in BrowserCrApplication sendEvent.
Revert ScopedTracker changes to  measure the jank in BrowserCrApplication sendEvent.

BUG=463272

Review URL: https://codereview.chromium.org/1440513006

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#359543}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk