[Annotations] The left part of the image is not visible when the browser is horizontally resized

[SoftVision-CosminMuntean]

[Affected versions]:

• Nightly 60.0a1
• Screenshots 31.2.0 stage

[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 stage 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.
3. Horizontally resize the browser until the respective scrollbar appears.
4. Observe the left part of the image.

[Expected result]:

• The image is fully visible.

[Actual results]:

• The left part of the image is not visible.

[Notes]:

• The issue is also reproducible if the browser is diagonally resized.
• Here is a screen recording with the issue:
  

[SoftVision-CosminMuntean]

Thanks @chenba for fixing this issue so quickly!

I have retested this issue on latest Screenshots (31.3.0) stage server and the issue is no longer reproducible. Tested on Windows 10 x64, Windows 7 x64, Arch Linux and Mac 10.12.

I also noticed that after this fix leaded, the image is no longer displayed on the center of the page in edit mode. We had an issue logged related to this: #3994, so I will reopen it for triage.