Use re2_fuzzer stored in re2 repository, remove old version.

third_party/re2/BUILD.gn

 # Copyright 2014 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.
 
+import("//testing/libfuzzer/fuzzer_test.gni")
+
 config("re2_config") {
   include_dirs = [ "src" ]
 }
 
 static_library("re2") {
   sources = [
     "src/re2/bitmap256.h",
     "src/re2/bitstate.cc",
     "src/re2/compile.cc",
     "src/re2/dfa.cc",
@@ skipping 35 matching lines @@
     "src/util/strutil.cc",
     "src/util/strutil.h",
     "src/util/utf.h",
     "src/util/util.h",
   ]
 
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
   public_configs = [ ":re2_config" ]
 }
+
+fuzzer_test("third_party_re2_fuzzer") {
+  sources = [
+    "src/re2/fuzzing/re2_fuzzer.cc",
+  ]
+  deps = [
+    ":re2",
+  ]
+}