The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a7608cf660f98528d51e73ad780b774b67258cd1

commit a7608cf660f98528d51e73ad780b774b67258cd1
Author: jsbell <jsbell@chromium.org>
Date: Tue Mar 22 06:27:56 2016

Measure usage of IDBFactory.webkitGetDatabaseNames()

Non-standard method; it would be nice to deprecate/remove this if usage
is low enough, or push for standardization if usage is too high.

BUG= 596543 
R=mpearson@chromium.com,philipj@opera.com

Review URL: https://codereview.chromium.org/1819943002

Cr-Commit-Position: refs/heads/master@{#382517}

[modify] https://crrev.com/a7608cf660f98528d51e73ad780b774b67258cd1/third_party/WebKit/Source/core/frame/UseCounter.h
[modify] https://crrev.com/a7608cf660f98528d51e73ad780b774b67258cd1/third_party/WebKit/Source/modules/indexeddb/IDBFactory.idl
[modify] https://crrev.com/a7608cf660f98528d51e73ad780b774b67258cd1/tools/metrics/histograms/histograms.xml

FWIW, an httparchive query shows the only use via this library:

https://github.com/agershun/alasql

... which handles the absence of the function.