Firefox accounts - change to white password show icon when button pressed

[cfogelSV]

Affected versions

• 75.0b10, 76.0a1 (2020-03-29)

Affected platforms

• macOS 10.15, Windows 10, Ubuntu 18.04;

Steps to reproduce

1. Launch Firefox, click to signin with any valid account and input the email address;
2. Click on the show password button after inputing anything in that string;

• after signing in;

3. Click on the Firefox account button;
4. Click on the Change password;
5. Input any password;
6. Click on the show password button.

Expected result

• icon is visible;

Actual result

• black icon in blue button;

Enhancement suggestion

• step 2 and 6:
• icon can be changed to white, such as buttons from Change/Add/Enable;

Regression range

• not a regression, most likely a scenario that was overlooked;

Additional notes

• as requested in bug 1625899

┆Issue is synchronized with this Jira Task
┆Issue Number: FXA-1523