Add a dummy //:chromium_builder_tests to the GN build.

BUILD.gn

 # Copyright (c) 2013 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.
 
 # This is the root build file for GN. GN will start processing by loading this
 # file, and recursively load all dependencies until all dependencies are either
 # resolved or known not to exist (which will cause the build to fail). So if
 # you add a new build file, there must be some path of dependencies from this
 # file to your new one or GN won't know about it.
 
@@ skipping 60 matching lines @@
 # TODO(GYP): This target exists for compatibility with GYP, specifically
 # for the iOS bots and the official builders.
 group("All") {
   testonly = true
 
   deps = [
     ":gn_all",
   ]
 }
 
+# TODO(GYP): This target exists for compatibility with GYP for the builders.
+# For now, this builds everything. We should decide if we want to build less.
+group("chromium_builder_tests") {
+  testonly = true
+
+  deps = [
+    ":All",
+  ],
+}
+
 # The "both_gn_and_gyp" target should reflect every target that is built
 # in both the GN and GYP builds, and ideally it should match the
 # "both_gn_and_gyp" target in build/gn_migration.gypi line-for-line.
 #
 # TODO(GYP): Add build steps that check and enforce this on the bots.
 group("both_gn_and_gyp") {
   testonly = true
   deps = [
     "//base:base_unittests",
     "//chrome/installer",
@@ skipping 810 matching lines @@
   assert(target_name != "")  # Mark as used.
   sources = invoker.actual_sources
   assert(
       sources == invoker.actual_sources,
       "Do not use a platform name in your output directory (found \"$root_build_dir\"). http://crbug.com/548283")
 }
 
 assert_valid_out_dir("_unused") {
   actual_sources = [ "$root_build_dir/foo" ]
 }