Needs metrics and a deprecation plan.

Metrics are https://www.chromestatus.com/metrics/feature/timeline/popularity/1273

Usage 0.001% until a few weeks ago when usage started spiking, but with bimodal numbers. The bimodal pattern seems similar to that seen with other APIs that were being used by analytics networks (rolling out/reverting a test), but I can't see them using this method...

We need to run an HTTPArchive search.

huh, looks like I analyzed this a year ago -  issue 596543 

HTTPArchive for 'webkitGetDatabaseNames' has only 42 hits. 
New usage is:

* Dexie.js - https://github.com/dfahlander/Dexie.js/search?utf8=%E2%9C%93&q=webkitgetdatabasenames
* AlaSQL - https://github.com/agershun/alasql/search?utf8=%E2%9C%93&q=webkitgetdatabasenames
* Mega - https://github.com/meganz/webclient/search?utf8=%E2%9C%93&q=webkitgetdatabasenames

To clarify... all the uses were of one of those libraries. Only a few uses of mega, most are dexie or alasql.

All three fall back appropriately in the absence of the function.

I think we should go ahead and deprecate (with message) and remove.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/af5e96b26ca62a309ee81a943721367a52b6741a

commit af5e96b26ca62a309ee81a943721367a52b6741a
Author: jsbell <jsbell@chromium.org>
Date: Thu Mar 02 12:36:19 2017

Deprecate IDBFactory webkitGetDatabaseNames()

Deprecation warning on the console, alerting to planned removal in M60.

BUG= 696010 

Review-Url: https://codereview.chromium.org/2723183002
Cr-Commit-Position: refs/heads/master@{#454237}

[modify] https://crrev.com/af5e96b26ca62a309ee81a943721367a52b6741a/third_party/WebKit/LayoutTests/fast/frames/sandboxed-iframe-storage-expected.txt
[modify] https://crrev.com/af5e96b26ca62a309ee81a943721367a52b6741a/third_party/WebKit/LayoutTests/http/tests/security/cross-origin-indexeddb-allowed-expected.txt
[modify] https://crrev.com/af5e96b26ca62a309ee81a943721367a52b6741a/third_party/WebKit/LayoutTests/http/tests/security/cross-origin-worker-indexeddb-allowed-expected.txt
[modify] https://crrev.com/af5e96b26ca62a309ee81a943721367a52b6741a/third_party/WebKit/LayoutTests/storage/indexeddb/factory-basics-expected.txt
[modify] https://crrev.com/af5e96b26ca62a309ee81a943721367a52b6741a/third_party/WebKit/LayoutTests/storage/indexeddb/factory-basics-workers-expected.txt
[modify] https://crrev.com/af5e96b26ca62a309ee81a943721367a52b6741a/third_party/WebKit/LayoutTests/storage/indexeddb/getdatabasenames-failed-open-expected.txt
[modify] https://crrev.com/af5e96b26ca62a309ee81a943721367a52b6741a/third_party/WebKit/Source/core/frame/Deprecation.cpp
[modify] https://crrev.com/af5e96b26ca62a309ee81a943721367a52b6741a/third_party/WebKit/Source/modules/indexeddb/IDBFactory.idl

Deprecated - now need to wait for M60 to remove.

Awesome! Thanks for doing this jsbell@! 

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4

commit 7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4
Author: jsbell <jsbell@chromium.org>
Date: Fri May 19 18:42:40 2017

Indexed DB: Remove nonstandard IDBFactory.webkitGetDatabaseNames()

Deprecated in M58, now removing in M60 per the plan.

Intent to Deprecate: https://groups.google.com/a/chromium.org/d/topic/blink-dev/2fUr-3wFPKI/discussion
Intent to Remove: https://groups.google.com/a/chromium.org/d/topic/blink-dev/A6m1Pt9-BAo/discussion
Chrome Status Entry: https://www.chromestatus.com/features/5725741740195840

BUG= 696010 

Review-Url: https://codereview.chromium.org/2818173003
Cr-Commit-Position: refs/heads/master@{#473255}

[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/content/browser/indexed_db/indexed_db_browsertest.cc
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/content/test/data/indexeddb/corrupted_open_db_detection.html
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/FlagExpectations/enable-blink-features=LayoutNG
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/fast/frames/resources/sandboxed-iframe-storage-disallowed.html
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/fast/frames/sandboxed-iframe-storage-expected.txt
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/http/tests/security/cross-origin-indexeddb-allowed-expected.txt
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/http/tests/security/cross-origin-worker-indexeddb-allowed-expected.txt
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/http/tests/security/resources/cross-origin-iframe-for-indexeddb.html
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/http/tests/security/resources/worker-for-indexeddb.js
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/http/tests/serviceworker/webexposed/global-interface-listing-service-worker-expected.txt
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/platform/mac/virtual/stable/http/tests/serviceworker/webexposed/global-interface-listing-service-worker-expected.txt
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/platform/mac/virtual/stable/webexposed/global-interface-listing-dedicated-worker-expected.txt
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/platform/mac/virtual/stable/webexposed/global-interface-listing-expected.txt
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/platform/mac/virtual/stable/webexposed/global-interface-listing-shared-worker-expected.txt
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/platform/win/virtual/stable/webexposed/global-interface-listing-expected.txt
[delete] https://crrev.com/f9d264174d41df066ab32166e4495f19da8c6d9c/third_party/WebKit/LayoutTests/storage/indexeddb/factory-basics-expected.txt
[delete] https://crrev.com/f9d264174d41df066ab32166e4495f19da8c6d9c/third_party/WebKit/LayoutTests/storage/indexeddb/factory-basics-workers-expected.txt
[delete] https://crrev.com/f9d264174d41df066ab32166e4495f19da8c6d9c/third_party/WebKit/LayoutTests/storage/indexeddb/factory-basics-workers.html
[delete] https://crrev.com/f9d264174d41df066ab32166e4495f19da8c6d9c/third_party/WebKit/LayoutTests/storage/indexeddb/factory-basics.html
[delete] https://crrev.com/f9d264174d41df066ab32166e4495f19da8c6d9c/third_party/WebKit/LayoutTests/storage/indexeddb/getdatabasenames-failed-open-expected.txt
[delete] https://crrev.com/f9d264174d41df066ab32166e4495f19da8c6d9c/third_party/WebKit/LayoutTests/storage/indexeddb/getdatabasenames-failed-open.html
[delete] https://crrev.com/f9d264174d41df066ab32166e4495f19da8c6d9c/third_party/WebKit/LayoutTests/storage/indexeddb/resources/factory-basics.js
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/virtual/service-worker-navigation-preload-disabled/http/tests/serviceworker/webexposed/global-interface-listing-service-worker-expected.txt
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/virtual/service-worker-navigation-preload-disabled/webexposed/global-interface-listing-dedicated-worker-expected.txt
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/virtual/service-worker-navigation-preload-disabled/webexposed/global-interface-listing-expected.txt
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/virtual/service-worker-navigation-preload-disabled/webexposed/global-interface-listing-shared-worker-expected.txt
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/virtual/service-worker-navigation-preload/http/tests/serviceworker/webexposed/global-interface-listing-service-worker-expected.txt
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/virtual/stable/http/tests/serviceworker/webexposed/global-interface-listing-service-worker-expected.txt
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/virtual/stable/webexposed/global-interface-listing-dedicated-worker-expected.txt
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/virtual/stable/webexposed/global-interface-listing-shared-worker-expected.txt
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/webexposed/global-interface-listing-dedicated-worker-expected.txt
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/webexposed/global-interface-listing-expected.txt
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/LayoutTests/webexposed/global-interface-listing-shared-worker-expected.txt
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/Source/core/frame/Deprecation.cpp
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/Source/modules/indexeddb/IDBFactory.cpp
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/Source/modules/indexeddb/IDBFactory.h
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/Source/modules/indexeddb/IDBFactory.idl
[modify] https://crrev.com/7a400ee2cb54a4be1a7b4dc6a3d407693d3699a4/third_party/WebKit/Source/modules/indexeddb/InspectorIndexedDBAgent.cpp

While I understand its design may be limited, I was hoping to work on a generic local IndexedDB browsing tool (beyond that in say DevTools).

Is any replacement planned to overcome the ascribed design flaws?

I've done an utility that uses NWJS so also Chromium.
The utility uses IndexedDB as database to store information. The user when the application starts can select between different databases that can create with the program (simply all databases that start with a prefix), here the use of webkitetDatabaseNames is opportune.

Is totally necessary remove that api?
Is any alternative?

Sorry, I can do it creating a indexedDB database with the list of the names of the indexedDB databases.
I must think before wrote..