Data saver prefs that record the daily content lengths are cleared if the current date is at least 1 day older than the last date when the prefs were written (Relevant code: https://cs.chromium.org/chromium/src/components/data_reduction_proxy/core/browser/data_reduction_proxy_compression_stats.cc?rcl=1477021054&l=258). However, some users may change date and time on their device for various reasons, and this may cause their data savings prefs to be completely erased (Example user feedback report: https://bugs.chromium.org/p/chromium/issues/detail?id=571470#c21). To measure how frequently this happens and to debug user feedback reports, Data saver should record the last date when the data savings were cleared as a UMA metric.
The following revision refers to this bug: https://chromium.googlesource.com/chromium/src.git/+/2c3ecceea409b42c873949bac0aa1acaa80451e3 commit 2c3ecceea409b42c873949bac0aa1acaa80451e3 Author: tbansal <tbansal@chromium.org> Date: Tue Dec 13 03:05:11 2016 Record DRP histogram on how long back savings were cleared Record Data Reduction Proxy (DRP) histogram on how long back savings were automatically cleared because the system clock moved back. If this happens too frequently, then we will need to add a mechanism to get around this. This would also help in debugging 0% savings feedback reports. BUG= 658354 Review-Url: https://codereview.chromium.org/2546273002 Cr-Commit-Position: refs/heads/master@{#438011} [modify] https://crrev.com/2c3ecceea409b42c873949bac0aa1acaa80451e3/components/data_reduction_proxy/core/browser/data_reduction_proxy_compression_stats.cc [modify] https://crrev.com/2c3ecceea409b42c873949bac0aa1acaa80451e3/components/data_reduction_proxy/core/browser/data_reduction_proxy_compression_stats_unittest.cc [modify] https://crrev.com/2c3ecceea409b42c873949bac0aa1acaa80451e3/components/data_reduction_proxy/core/browser/data_reduction_proxy_prefs.cc [modify] https://crrev.com/2c3ecceea409b42c873949bac0aa1acaa80451e3/components/data_reduction_proxy/core/browser/data_reduction_proxy_settings.cc [modify] https://crrev.com/2c3ecceea409b42c873949bac0aa1acaa80451e3/components/data_reduction_proxy/core/browser/data_reduction_proxy_settings.h [modify] https://crrev.com/2c3ecceea409b42c873949bac0aa1acaa80451e3/components/data_reduction_proxy/core/browser/data_reduction_proxy_settings_unittest.cc [modify] https://crrev.com/2c3ecceea409b42c873949bac0aa1acaa80451e3/components/data_reduction_proxy/core/common/data_reduction_proxy_pref_names.cc [modify] https://crrev.com/2c3ecceea409b42c873949bac0aa1acaa80451e3/components/data_reduction_proxy/core/common/data_reduction_proxy_pref_names.h [modify] https://crrev.com/2c3ecceea409b42c873949bac0aa1acaa80451e3/tools/metrics/histograms/histograms.xml
Comment 1 by bengr@chromium.org
, Oct 28 2016