Migrate to NOTREACHED() in ui/

NOTREACHED() and NOTREACHED_IN_MIGRATION() are both CHECK-fatal now.
The former is [[noreturn]] so this CL also performs dead-code removal
after the NOTREACHED().

This CL does not attempt to do additional rewrites of any surrounding
code, like:

if (!foo) {
  NOTREACHED();
}

to CHECK(foo);

Those transforms take a non-trivial amount of time (and there are
thousands of instances). Cleanup can be left as an exercise for the
reader.

Bug: 40580068
Change-Id: Ib1ec65c775c4c64f0dffc002c232000d3688a2fb
Cq-Include-Trybots: luci.chromium.try:linux-dcheck-off-rel
Low-Coverage-Reason: OTHER Should-be-unreachable code
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5975073
Commit-Queue: Peter Boström <[email protected]>
Reviewed-by: Sam McNally <[email protected]>
Reviewed-by: Mitsuru Oshima <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1375585}
diff --git a/ui/display/display_transform.cc b/ui/display/display_transform.cc
index 2af5770f..de6fa79 100644
--- a/ui/display/display_transform.cc
+++ b/ui/display/display_transform.cc
@@ -38,8 +38,7 @@
     case display::Display::ROTATE_270:
       return gfx::OVERLAY_TRANSFORM_ROTATE_CLOCKWISE_270;
   }
-  NOTREACHED_IN_MIGRATION();
-  return gfx::OVERLAY_TRANSFORM_NONE;
+  NOTREACHED();
 }
 
 }  // namespace display