[Annotations] "Color Picker" panel is no longer visible

[SoftVision-CosminMuntean]

[Affected versions]:

• Nightly 60.0a1
• Screenshots 28.0.0 dev

[Affected Platforms]:

• All Windows
• All Mac
• All Linux

[Prerequisites]:

• The "xpinstall.signatures.required" boolean pref is set to "false".
• The "extensions.legacy.enabled" boolean pref is set tot "true".
• Have the Screenshots dev version installed on a new clean profile.
• Have a saved shot link.

[Steps to reproduce]:

1. Open Firefox browser with the profile from prerequisites and navigate to the saved shot link.
2. Click the "Edit This Image" button and click the "Crop" tool.
3. Click the "Color Picker" button.
4. Observe the "Color Picker" panel.

[Expected result]:

• The "Color Picker" panel is entirely visible.

[Actual results]:

• The "Color Picker" panel is opened under the background and is not entirely visible.

[Additional Notes]:

• Here is a screen recording with the issue:
  

[SoftVision-CosminMuntean]

This issue is no longer reproducible on latest Screenshots 28.0.0 dev version. Tested on Windows 7 x64, Mac 10.13 and Arch Linux.