Fix chrome target in Windows GN build.

components/invalidation/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.
 if (is_android) {
   import("//build/config/android/rules.gni")
 }
 
 static_library("invalidation") {
   sources = [
     "ack_handle.cc",
@@ skipping 90 matching lines @@
     sources += [
       "android/component_jni_registrar.cc",
       "android/component_jni_registrar.h",
       "invalidation_service_android.cc",
       "invalidation_service_android.h",
     ]
     deps += [ ":jni_headers" ]
   }
 }
 
-static_library("unittests") {
+group("unittests") {
   testonly = true
-  sources = []
   deps = [
     ":invalidation",
     ":test_support",
   ]
   if (is_android) {
     deps += [
       ":javatests",
       ":jni_headers",
     ]
   }
@@ skipping 69 matching lines @@
     ]
     DEPRECATED_java_in_dir = "android/javatests/src"
   }
   generate_jni("jni_headers") {
     sources = [
       "android/java/src/org/chromium/components/invalidation/InvalidationService.java",
     ]
     jni_package = "components/invalidation"
   }
 }