Remove redundant check in GCTracer::SampleAllocation.
Remove redundant check in GCTracer::SampleAllocation.

BUG=

Review URL: https://codereview.chromium.org/1213593004

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#29443}

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh