This is a follow up to bug 1564655. It removes the offset from ToDeviceSpace
and thus moves item rects into absolute space which is now the same coordinate
space as the recordings are in.
We also adjust item bounds for fallback blobs.
Some additional changes that need happen to:
1. In Moz2DImageRenderer we can reunify the origin because the recording and
the recording metadata return to using the same coordinate space.
2. The calls to PushLayer can return to using the item bounds
which are now in the same coordinate space.
3. This dirty rect which remains in images space is adjusted during merging.
Differential Revision: https://phabricator.services.mozilla.com/D38015
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extra : moz-landing-system : lando
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