RELAND: Enable jpeg_decode_accelerator_unittest in chromiumos_preflight

The original CL crrev.com/c/1199580 was reverted in crrev.com/c/1204599
because it broke windows compilation (File path literals etc).
This CL limits the compilation to linux and chromeos: the new changes
can be seen in crrev.com/c/1206675e/1..2

TBR=jbudorick@chromium.org, sandersd@chromium.org since the changes
are trivial re. the previous CL.

Original CL description -----------------------------------------------

jpeg_decode_accelerator_unittest is compiled and run on the CrOs
autotest infra, but is not compiled on the bots, when it possibly
should. This CL adds that target to the chromiumos_preflight of
the top level BUILD.gn.

Bug: 732531, 877694

Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Reviewed-on: https://chromium-review.googlesource.com/1199580Reviewed-by: Ben Pastene <bpastene@chromium.org>
Reviewed-by: Dan Sanders <sandersd@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Miguel Casas <mcasas@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#588635}
Change-Id: Ic71fc5076484d30dda90654cd5501aa802258feb
Reviewed-on: https://chromium-review.googlesource.com/1206675Reviewed-by: Miguel Casas <mcasas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#589051}

BUILD.gn

@@ -817,6 +817,7 @@ if (is_chromeos) {
       "//chrome",
       "//chrome/test/chromedriver",
       "//media:media_unittests",
+      "//media/gpu:jpeg_decode_accelerator_unittest",
       "//ppapi/examples/video_decode",
       "//sandbox/linux:chrome_sandbox",
       "//sandbox/linux:sandbox_linux_unittests",

media/gpu/BUILD.gn

@@ -531,7 +531,7 @@ if (use_vaapi) {
   }
 }
 
-if (use_v4l2_codec || use_vaapi) {
+if (is_chromeos || is_linux) {
   test("jpeg_decode_accelerator_unittest") {
     deps = [
       "//base",