[libfuzzer] support multiple seed_corpus directories.

testing/libfuzzer/fuzzer_test.gni

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Defines fuzzer_test.
 #
 import("//build/config/features.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//testing/test.gni")
 
@@ skipping 19 matching lines @@
   if (!disable_libfuzzer &&
       (use_libfuzzer || use_afl || use_drfuzz || is_linux)) {
     assert(defined(invoker.sources), "Need sources in $target_name.")
 
     test_deps = [ "//testing/libfuzzer:libfuzzer_main" ]
 
     if (defined(invoker.deps)) {
       test_deps += invoker.deps
     }
 
-    if (defined(invoker.seed_corpus)) {
+    if (defined(invoker.seed_corpus) || defined(invoker.seed_corpuses)) {
+      assert(!(defined(invoker.seed_corpus) && defined(invoker.seed_corpuses)),
+             "Do not use both seed_corpus and seed_corpuses for $target_name.")
+
       out = "$root_build_dir/$target_name" + "_seed_corpus.zip"
 
       action(target_name + "_seed_corpus") {
         script = "//testing/libfuzzer/archive_corpus.py"
+
         args = [
-          "--corpus",
-          rebase_path(invoker.seed_corpus),
           "--output",
           rebase_path(out),
         ]
 
+        if (defined(invoker.seed_corpus)) {
+          args += [ rebase_path(invoker.seed_corpus) ]
+        }
+
+        if (defined(invoker.seed_corpuses)) {
+          foreach(seed_corpus_path, invoker.seed_corpuses) {
+            args += [ rebase_path(seed_corpus_path) ]
+          }
+        }
+
         outputs = [
           out,
         ]
+
         deps = [
           "//testing/libfuzzer:seed_corpus",
         ]
       }
 
       test_deps += [ ":" + target_name + "_seed_corpus" ]
     }
 
     if (defined(invoker.dict) || defined(invoker.libfuzzer_options)) {
       if (defined(invoker.dict)) {
@@ skipping 78 matching lines @@
       assert(invoker.seed_corpus == [] || invoker.seed_corpus != [])
     }
     assert(!defined(invoker.check_includes) || invoker.check_includes != [])
     assert(!defined(invoker.include_dirs) || invoker.include_dirs != [])
     assert(!defined(invoker.defines) || invoker.defines != [])
 
     group(target_name) {
     }
   }
 }