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Each Ozone platform creates its own NativeDisplayDelegate to get
display information. Otherwise, 'display::FakeDisplayDelegate' is
used for NativeDisplayDelegate.

Per bug, ozone headless is crashing because it uses
FakeDisplayDelegate and it doesn't invoke OnConfigurationChanged
before initialization completes so ScreenBase can't add the display.
Once NativeDisplayDelegate is initialized, DesktopScreenOzone
requires DisplayMode from DisplaySnapshot but FakeDisplayDelegate has
FakeDisplaySnapshot and it doesn't have DisplayMode.

This CL creates HeadlessNativeDisplayDelegate which owns
DisplaySnapshot and DisplayMode for ozone/headless.
DesktopScreenOzone keeps it in delegate_ and communicates with it.

To try this, compile with the following gn args
use_ozone = true
ozone_platform_headless = true

TEST=./out/Debug/chrome --ozone-platform=headless

Bug: 851375
Change-Id: I2c097bf54fafb2d9311919647801e401c59ba929
Reviewed-on: https://chromium-review.googlesource.com/1120447
Commit-Queue: Julie Jeongeun Kim <jkim@igalia.com>
Reviewed-by: Michael Spang <spang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572488}