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This creates a new session with the system compositor (Scenic) and uses
it to create the vulkan surface resources. This is necessary in order to
support vulkan surfaces from the GPU process, since the browser Scenic
session will not be accessible there.

In order for this to work, we need to be able to run platform code when a
gpu::VulkanSurface is destroyed. To accomplish this, this adds a
destruction callback to gpu::VulkanSurface which cleans up the Scenic
resources associated with the surface.

Bug: 861853
Test: run_content_shell --ozone-platform=scenic --disable-gpu --enable-vulkan

Change-Id: If08c25746ba73569afae63040a7f6551861eeaad
Reviewed-on: https://chromium-review.googlesource.com/c/1343238
Commit-Queue: Michael Spang <spang@chromium.org>
Reviewed-by: Robert Kroeger <rjkroege@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611830}