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High memory usage is forced by duplicate tabs in the same process.

BUG=
CQ_EXTRA_TRYBOTS=tryserver.chromium.perf:linux_perf_bisect;tryserver.chromium.perf:mac_perf_bisect;tryserver.chromium.perf:win_perf_bisect;tryserver.chromium.perf:android_nexus5_perf_bisect

Review URL: https://codereview.chromium.org/1145173002

Cr-Commit-Position: refs/heads/master@{#330930}