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**What kind of change does this PR introduce?**
- adds missing golden asset for firefox
**Summary**
- This change will let us see in mozilla ci, where we don't skip this
test, a better error message. Right now it fails with missing asset
error.
**Does this PR introduce a breaking change?**
no
This corresponds to Chromium 90.0.4403.0
This roll includes:
- Cut screenshot by ViewPort size, not position (crrev.com/c/2643792)
BREAKING CHANGE:
- `page.screenshot` cuts screenshot content by the ViewPort size, not ViewPort position.
