Gradient background option for NTP

[sangwoo108]

subtask of #15252. Overall design also can be found there.

Spec:

• Users can choose a gradient background for NTP
• This will be applied only to the current local machine.
• When Users choose another option like custom background and brave background, the background should be changes to it.

[MadhaviSeelam]

Verification PASSED

Brave | 1.45.80 Chromium: 106.0.5249.65 (Official Build) beta (64-bit)
-- | --
Revision | 3269dc3633cdd2ab94546fdbe54962e45b17a6e0-refs/branch-heads/5249@{#580}
OS | Windows 11 Version 21H2 (Build 22000.978)

Case 1: Toggle ON Refresh on every new tab

1. installed 1.45.80
2. launched Brave
3. opened a new-tab page
4. clicked on Customize
5. clicked on Gradients card
6. toggle ON Refresh on every new tab
7. open NTP

Confirmed when Refresh on every new tab toggle is on, Gradient background is picked on every new tab

step 5-6	step 7

Case 2: Toggle OFF Refresh on every new tab

1. click customize on the last tab from Case 1
2. click on selected Gradients card to return to Refresh on every new tab
3. toggle OFF Refresh on every new tab
4. open NTP

Confirmed same Gradient background is picked from the last tab in Case 1 for each new tab

Ex1	Ex2

[stephendonner]

Verification IN-PROGRESS using

Brave	1.45.84 Chromium: 106.0.5249.91 (Official Build) beta (x86_64)
Revision	fa96d5f07b1177d1bf5009f647a5b8c629762157-refs/branch-heads/5249@{#707}
OS	macOS Version 11.7 (Build 20G817)

Case 1: Toggle ON Refresh on every new tab - PASSED

1. installed 1.45.84
2. launched Brave
3. opened a new-tab page
4. clicked on Customize
5. clicked on Gradients card
6. toggle ON Refresh on every new tab
7. open NTP

Confirmed when Refresh on every new tab toggle is on, a new Gradient background is picked on each new (non-Sponsored-Image) tab

step 5-6	step 7, 1	2	3	4

Case 2: Toggle OFF Refresh on every new tab - PASSED

1. clicked Customize on the last tab from Case 1
2. clicked on selected Gradients card to return to Refresh on every new tab
3. toggled Refresh on every new tab to OFF
4. opened a bunch of new-tab pages

Confirmed same Gradient background is picked from the last tab in Case 1 for each new tab

step 1	step 2	step 3	step 4, 1	2

---

Verification passed on

Brave	1.45.90 Chromium: 106.0.5249.103 (Official Build) beta (64-bit)
Revision	182570408a1f25ab2731ef5f283b918df9b9f956-refs/branch-heads/5249_91@{#6}
OS	Ubuntu 18.04 LTS

Case 1: Toggle ON Refresh on every new tab - PASSED

1. installed 1.45.x
2. launched Brave
3. opened a new-tab page
4. clicked on Customize
5. clicked on Gradients card
6. toggle ON Refresh on every new tab
7. open NTP

Confirmed when Refresh on every new tab toggle is on, a new Gradient background is picked on each new (non-Sponsored-Image) tab

Case 2: Toggle OFF Refresh on every new tab - PASSED

1. clicked Customize on the last tab from Case 1
2. clicked on selected Gradients card to return to Refresh on every new tab
3. toggled Refresh on every new tab to OFF
4. opened a bunch of new-tab pages

Confirmed same Gradient background is picked from the last tab in Case 1 for each new tab