GitLab

This addresses two shortcomings of PlayerCompositorDelegate for the
Long Screenshots use case:
1. An in-memory PaintPreviewProto is provided from Java rather than one
   from disk.
2. Compositing should occur to a single SkPicture using the MainFrame
   mode of the compositor rather than the SeparateFrame mode.

This CL also makes the MainFrame mode return the dimensions of the
SkPicture so that Long Screenshot can leverage this information.

Change-Id: If0b2d666f7459b94f4501c23808c504826a0112a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2578076Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Reviewed-by: Mehran Mahmoudi <mahmoudi@chromium.org>
Commit-Queue: Calder Kitagawa <ckitagawa@chromium.org>
Cr-Commit-Position: refs/heads/master@{#835290}