Bugzilla

**Affected versions**
* 75.0a1 (2020-03-04), 74.0;

**Affected platforms**
* Windows 10, macOS 10.15

**Steps to reproduce**
1. Launch Firefox;
2. Access about:downloads 
3. Click on the HambourgerMenu button;
4. Click on the Customize button;
5. Click on the Themes button;
6. Click on the one opposing your current theme ( Light vs Dark );
7. Restart the browser and access about:downloads

**Expected result**
* theme is updated;

**Actual result**
* theme inside the page remains the same, not updated after changing it;

**Regression range**
* will provide one asap;

**Additional notes**
* attached recording with the issue(Windows 10 - dark theme;
* issue noticed with Windows10 - dark theme, macOS 10.15 - light theme.

**Affected versions**
* 75.0a1 (2020-03-04), 74.0;

**Affected platforms**
* Windows 10, macOS 10.15, Ubuntu 19.04;

**Steps to reproduce**
1. Launch Firefox;
2. Access about:downloads 
3. Click on the HambourgerMenu button;
4. Click on the Customize button;
5. Click on the Themes button;
6. Click on the one opposing your current theme ( Light vs Dark );
7. Restart the browser and access about:downloads

**Expected result**
* theme is updated;

**Actual result**
* theme inside the page remains the same, not updated after changing it;

**Regression range**
* will provide one asap;

**Additional notes**
* attached recording with the issue(Windows 10 - dark theme;
* issue noticed with Windows10/Ubuntu19 - dark theme, macOS 10.15 - light theme.