Log pref file size histogram on read rather than on write.
All we care about is the size of the file per user, logging it on write
was wrong as it would generate WAY too many reports as indicated by
issue 453454.
Also changed the distribution to be logarithmic rather than linear to
give better insights (with a linear distribution all we could see was that
most people were below 209KB but we didn't have finer buckets below that).
BUG=453454, 355722
Review URL: https://codereview.chromium.org/891663003
Cr-Commit-Position: refs/heads/master@{#314064}
CrOS-Libchrome-Original-Commit: f16b59a08d0a0d8587cd968084a75f6e30799787
3 files changed