[Annotations] The text caret wrongly disappears after the string color is changed

[Softvision-CristinaBadescu]

[Affected versions]:

• Nightly 63.0a1
• Dev Edition 62.0b7
• Release 61.0.1 Unbranded

[Affected Platforms]:

• All Windows
• All Mac
• All Linux

[Prerequisites]:

• Have a clean Firefox profile with the latest Firefox Screenshots v33.0.0dev installed.
• Have a saved shot link.

[Steps to reproduce]:

1. Open the Firefox browser with the profile from prerequisites and navigate to the saved shot link.
2. Click the "Edit this image" button and click the "Add text" button.
3. Click the "Color Picker" button and change the color.
4. Observe the behavior.

[Expected result]:

• The color is changed and the text caret is displayed in the text box.

[Actual result]:

• The color is changed but the text caret disappears from the text box.

[Notes]:

• This issue is not reproducible if you change the text size.
• Here is a screen recording with this issue:
  

[Softvision-CristinaBadescu]

This issue is no longer reproducible using the latest Firefox Screenshots dev version installed from here, on latest Nightly build 63.0a1. Verified on Windows 10 x64, Mac 10.13.5 and Arch Linux 4.12.

However, if you type a string and change the color, the text caret is displayed at the beginning of it. This behavior is tracked in bug #4642.