build: run gen_fuzzer_owners in a shallow pool.

Bug: 1008734
Change-Id: If035ff53997e314e1c7ade677d99af6088f82e18
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1838292Reviewed-by: Max Moroz <mmoroz@chromium.org>
Commit-Queue: John Budorick <jbudorick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702587}

testing/libfuzzer/BUILD.gn

@@ -53,3 +53,9 @@ config("no_clusterfuzz") {
 # noop to tag seed corpus rules.
 source_set("seed_corpus") {
 }
+
+if (use_fuzzing_engine) {
+  pool("fuzzer_owners_pool") {
+    depth = 1
+  }
+}

testing/libfuzzer/fuzzer_test.gni

@@ -38,10 +38,14 @@ template("fuzzer_test") {
     assert(defined(invoker.sources), "Need sources in $target_name.")
 
     test_deps = [ "//testing/libfuzzer:libfuzzer_main" ]
+    test_data_deps = []
 
     if (defined(invoker.deps)) {
       test_deps += invoker.deps
     }
+    if (defined(invoker.data_deps)) {
+      test_data_deps += invoker.data_deps
+    }
 
     if (defined(invoker.seed_corpus) || defined(invoker.seed_corpuses)) {
       assert(!(defined(invoker.seed_corpus) && defined(invoker.seed_corpuses)),
@@ -157,6 +161,7 @@ template("fuzzer_test") {
       owners_file_name = target_name + ".owners"
       action(owners_file_name) {
         script = "//testing/libfuzzer/gen_fuzzer_owners.py"
+        pool = "//testing/libfuzzer:fuzzer_owners_pool"
         args = [
           "--owners",
           rebase_path("$root_build_dir/" + owners_file_name, root_build_dir),
@@ -181,7 +186,7 @@ template("fuzzer_test") {
           "$root_build_dir/$owners_file_name",
         ]
       }
-      test_deps += [ ":" + owners_file_name ]
+      test_data_deps += [ ":" + owners_file_name ]
     }
 
     test(target_name) {
@@ -196,6 +201,7 @@ template("fuzzer_test") {
                                "libs",
                              ])
       deps = test_deps
+      data_deps = test_data_deps
 
       if (defined(invoker.additional_configs)) {
         configs += invoker.additional_configs