Adding perf test isolate and gn build target for swarming the benchmarks.

tools/perf/BUILD.gn

 # 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.
 
 group("perf") {
   testonly = true
   deps = [
     "//tools/perf/chrome_telemetry_build:telemetry_chrome_test",
   ]
 
   data = [
     "//tools/perf/",
 
     # Field trial config
     "//tools/variations/",
     "//testing/variations/",
+
+    # For blink_perf benchmarks.
+    "//third_party/WebKit/PerformanceTests/",
+
+    # For blink_perf.BlinkPerfPywebsocket benchmark.
+    "//third_party/pywebsocket/",
   ]
 }
 
 if (is_android) {
   import("//build/config/android/rules.gni")
 
   wrapper_script("run_benchmark_wrapper") {
     target = "run_benchmark"
     flag_name = "--chromium-output-directory"
   }
 }