Disable unit tests using --gtest-filter instead of at compile time (flutter/engine#16472)

engine/src/flutter/fml/BUILD.gn

@@ -230,9 +230,14 @@ executable("fml_unittests") {
   sources = [
     "base32_unittest.cc",
     "command_line_unittest.cc",
+    "file_unittest.cc",
     "gpu_thread_merger_unittests.cc",
     "memory/ref_counted_unittest.cc",
     "memory/weak_ptr_unittest.cc",
+    "message_loop_task_queues_merge_unmerge_unittests.cc",
+    "message_loop_task_queues_unittests.cc",
+    "message_loop_unittests.cc",
+    "message_unittests.cc",
     "paths_unittests.cc",
     "platform/darwin/string_range_sanitization_unittests.mm",
     "synchronization/count_down_latch_unittests.cc",
@@ -246,23 +251,6 @@ executable("fml_unittests") {
     "time/time_unittest.cc",
   ]
 
-  # TODO(https://github.com/flutter/flutter/issues/50032) Enable after the
-  # Fuchsia message loop migration is complete.
-  if (!is_fuchsia) {
-    sources += [
-      "message_loop_task_queues_merge_unmerge_unittests.cc",
-      "message_loop_task_queues_unittests.cc",
-      "message_loop_unittests.cc",
-      "message_unittests.cc",
-    ]
-  }
-
-  # TODO(https://github.com/flutter/flutter/issues/50031):
-  # Figure out why these tests don't work currently on Fuchsia
-  if (!is_fuchsia) {
-    sources += [ "file_unittest.cc" ]
-  }
-
   deps = [
     ":fml_fixtures",
     "//flutter/fml",

engine/src/flutter/testing/fuchsia/run_tests.sh

@@ -49,9 +49,12 @@ done
     -f flutter_runner_scenic_tests-0.far  \
     -t flutter_runner_scenic_tests
 
+# TODO(https://github.com/flutter/flutter/issues/50032) Enable after the
+# Fuchsia message loop migration is complete.
 ./fuchsia_ctl -d $device_name test \
     -f fml_tests-0.far  \
-    -t fml_tests
+    -t fml_tests \
+    -a "--gtest_filter=-MessageLoop*:Message*:FileTest*"
 
 ./fuchsia_ctl -d $device_name test \
     -f flow_tests-0.far  \