Re-land: telemetry: Add a page set for blink's memory usage measurement

Added decorator as a workaround for crbug.com/532075

Original description:

The page set will be used as metrics for tracking memory
reduction efforts on Blink. Details can be found at [1].

[1] https://docs.google.com/document/d/1zlGQkwkWEu5LUg-CrZHHRuhDtZcuvrRv8bjdC8-noaU/edit?usp=sharing

TBR=nednguyen,perezju
BUG=524338
CQ_EXTRA_TRYBOTS=tryserver.chromium.perf:android_nexus5_perf_bisect

Review URL: https://codereview.chromium.org/1343193002

Cr-Commit-Position: refs/heads/master@{#349079}