This commit adds a CrossProcessPaint class which can be used to paint a
cross process document tree. This API is async, as we cannot block on child
processes, and initially geared towards servicing a JS API and not internal
consumers. The API can only be used in the chrome process for security
reasons.
The class is implemented as a recursive resolver, requesting a root paint,
gathering dependent frames to be painted, then requesting paints from those
tabs. Once all paints have been completed, the dependency tree is rasterized
in a bottom up fashion.
Future improvements can be made here. Currently, the rasterization is
performed on the main thread which could cause jank. We also transmit
recordings directly over IPDl, and no effort is made to minimize the
recordings from child layer trees.
Differential Revision: https://phabricator.services.mozilla.com/D6790
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extra : rebase_source : b213de269b33486552ddc0be17207f9fb3f78c9c
Sylvestre Ledru
Ryan Hunt