Add chrome perf tests and sniffer to GN build.

chrome/tools/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.
 
-group("mojo") {
-  public_deps = [
-    "//media/mojo/interfaces",
-    "//media/mojo/services",
+# This target just provides references to the Chrome tools to bring them into
+# the build.
+group("tools") {
+  testonly = true
+  deps = [
+    "//chrome/tools/service_discovery_sniffer",
   ]
 }
-
-group("tests") {
-  testonly = true
-  deps = [
-    "//media/mojo/services:tests"
-  ]  
-}