Fix flaky build in chromeos-arm[64]-generic-rel/dbg

I guess the problem is because the gpu_preferences_mojom_traits.h
doesn't depends on "ui/base:features", so gpu_preferences_mojom_traits.h
may get used before ui/base/buildflags.h is generated.

Bug: 1106530
Change-Id: Ieb7b9dd34ffe217bcd7cf9f71d5d75e0e483e172
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2304770
Commit-Queue: Peng Huang <penghuang@chromium.org>
Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#789618}

gpu/ipc/common/BUILD.gn

@@ -509,6 +509,9 @@ mojom("gpu_preferences_interface") {
       ]
       traits_headers = [ "gpu_preferences_mojom_traits.h" ]
       traits_public_deps = [ "//media:media_buildflags" ]
+      if (use_ozone) {
+        traits_public_deps += [ "//ui/base:features" ]
+      }
       traits_deps = [
         # We depend on gpu_preferences but since it also depends on its own
         # mojo bindings, that is handled with an |allowed_circular_includes|