The "Copy" and "Download" strings from the preview shot wrongly exceed the buttons' area, if the browser is horizontally resized to the maximum

[SoftVision-CosminMuntean]

[Notes]:

• The issue is more visible on localized builds with languages that have long strings (eg: German).

[Affected versions]:

• Firefox 66.0a1
• Screenshots 37.0.0 dev version

[Affected Platforms]:

• All Windows
• All Mac
• All Linux

[Prerequisites]:

• Have a German Nightly (66.0a1) build installed or extracted.
• Have the latest Screenshots (37.0.0) dev version installed on a Firefox profile.

[Steps to reproduce]:

1. Open Nightly browser from prerequisites and navigate to any website.
2. Click the "Take a Screenshot" button from "Page Actions" menu.
3. Click the "Save full page" or "Save Visible" button from the top right corner of the page.
4. Horizontally resize the browser to the maximum.
5. Observe the "Copy" and "Download" buttons.

[Expected result]:

• The buttons are correctly displayed.

[Actual result]:

• The "Copy" and "Download" strings wrongly exceed the buttons' area.

[Additional Notes]:

• Here is a screenshot using a German build:

• Here is a screenshot using an English build: