Add chrome perf tests and sniffer to GN build.

chrome/tools/BUILD.gn

Index: chrome/tools/BUILD.gn
diff --git a/media/mojo/BUILD.gn b/chrome/tools/BUILD.gn
similarity index 55%
copy from media/mojo/BUILD.gn
copy to chrome/tools/BUILD.gn
index d30848b19213bbd641e751c20fcd5be3dc8a6191..94f11750a46e59c5002ae969eb3c8a22506b3d7e 100644
--- a/media/mojo/BUILD.gn
+++ b/chrome/tools/BUILD.gn
@@ -2,16 +2,11 @@
 # 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",
-  ]
-}
-
-group("tests") {
+# This target just provides references to the Chrome tools to bring them into
+# the build.
+group("tools") {
   testonly = true
   deps = [
-    "//media/mojo/services:tests"
-  ]  
+    "//chrome/tools/service_discovery_sniffer",
+  ]
 }