Sites are never added to auto-contribute list if rewards are enabled through Rewards Panel

[btlechowski]

Steps to Reproduce

1. Clean install
2. Enable rewards through Rewards Panel (Rewards icon)
3. Open twitch.tv in a new tab and watch a stream for few minutes
4. Close twitch.tv tab
5. Go to brave://rewards/ and check auto-contribute list.

Important: Sites will be added to auto-contribute list only after brave://rewards/ is opened first.

Actual result:

auto-contribute list is empty.
the publisher is not added to publisher_info_db

Steps 1-3

Steps 4-5 after 5 minutes of watching stream.

Expected result:

the twitch publisher is added to auto-contribute list

Reproduces how often:

always

Brave version (brave://version info)

Brave	0.55.18 Chromium: 70.0.3538.67 (Official Build) (64-bit)
Revision	9ab0cfab84ded083718d3a4ff830726efd38869f-refs/branch-heads/3538@{#1002}
OS	Windows 7 x64

Reproduced by @LaurenWags on Mac OS
cc @GeetaSarvadnya @kjozwiak @srirambv @NejcZdovc

[GeetaSarvadnya]

Verification Passed on

Brave	0.57.3 Chromium: 70.0.3538.67 (Official Build) dev (64-bit)
Revision	9ab0cfab84ded083718d3a4ff830726efd38869f-refs/branch-heads/3538@{#1002}
OS	Windows

Went through verification using the following build under macOS 10.13.6 x64 - PASSED

Brave	0.55.21 Chromium: 70.0.3538.77 (Official Build) (64-bit)
Revision	0f6ce0b0cd63a12cb4eccea3637b1bc9a29148d9-refs/branch-heads/3538@{#1039}
OS	Mac OS X

• ensured that YT, Twitch and websites were being added when enabling rewards via the panel
• also ensured that they appeared under publisher_info_db

Verification Passed on

Brave	0.56.8 Chromium: 70.0.3538.77 (Official Build) (64-bit)
Revision	0f6ce0b0cd63a12cb4eccea3637b1bc9a29148d9-refs/branch-heads/3538@{#1039}
OS	Linux

• Verified publishers are listed when rewards enabled via panel
• Verified listed publisher appear in publisher_info_db as well