GitLab

Currently, docked magnifier container is nested inside containers that
have contents to be magnified, essentially creating a cycle (magnifier
magnifying itself). Since docked magnifier uses ui::Reflector, it is not
an issue because ui::Reflector is one frame behind, magnifying the
previous frame. However, ui::Refelctor does not work with out-of-process
display compositor (OOP-D).

Our solution to the OOP-D case is to update generated compositor frame
to create a RenderPass for the magnified content and refer to that
RenderPass twice in the compositor frame: once where the content should
appear normally, and once inside the magnified viewport. This way the
magnifier is not one frame behind anymore, however, we need to break the
cycle mentioned above. To remove the cycle, this CL creates a container
for the magnified content (called MagnifiedContainer) and makes the
DockedMagnifierContainer a sibling of this new container.

BUG=947565

Change-Id: Id8d685f90667eac0302b788ffc6d17d02fb79435
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1628909Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Commit-Queue: Mohsen Izadi <mohsen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#664302}