[Safari] The progress starts from random places on the upload circle

[SoftVision-CarmenFat]

[Affected versions]:

• Safari 11.0.3

[Affected Platforms]:

• All Mac

[Steps to reproduce]:

1. Start Safari browser and navigate to "https://send.stage.mozaws.net/" page.
2. Upload a file and observe the progress.

[Expected result]:

• The progress starts from the middle top part on the upload circle.

[Actual results]:

• The progress starts from random places on the upload circle.

[Notes]:

• This issue is also reproducible on https://send.dev.mozaws.net/.
• This is not reproducible when downloading a file.
• Here is a screen recording of the issue: https://goo.gl/ecWtG6

[SoftVision-CarmenFat]

I have verified that the issue is no longer reproducible on Dev and Stage servers using Mac 10.13.