Bug 1581677 - Fix consistency bug in WR dirty rect calculation. r=nical
Bug 1581677 - Fix consistency bug in WR dirty rect calculation. r=nical

This fixes a case where the is_same_content field was no longer
being reset to true before dependency calculation could occur.

In some cases, this could result in a tile being updated, but
the dirty rect being empty, which meant all primitives in that
tile would fail the visibility culling test.

Differential Revision: https://phabricator.services.mozilla.com/D46247

[wrupdater] From https://hg.mozilla.org/mozilla-central/rev/43d18e14f370881d534e376bd7322579ecb81c9b

servo/webrender,servo/webrender,servo/webrender,servo/webrender,servo/webrender,servo/webrender