Add support for robolectric play-services-shadows.

testing/android/junit/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.
 
 assert(is_android)
 
 import("//build/config/android/rules.gni")
 
 java_library("junit_test_support") {
+  # Skip platform checks since Robolectric depends on requires_android targets.
+  bypass_platform_checks = true
   testonly = true
   java_files = [
     "java/src/org/chromium/testing/local/AnnotationProcessor.java",
     "java/src/org/chromium/testing/local/BackgroundShadowAsyncTask.java",
     "java/src/org/chromium/testing/local/CustomShadowAsyncTask.java",
     "java/src/org/chromium/testing/local/GtestComputer.java",
     "java/src/org/chromium/testing/local/GtestFilter.java",
     "java/src/org/chromium/testing/local/GtestListener.java",
     "java/src/org/chromium/testing/local/GtestLogger.java",
     "java/src/org/chromium/testing/local/JsonListener.java",
@@ skipping 13 matching lines @@
 }
 
 junit_binary("junit_unit_tests") {
   java_files = [
     "javatests/src/org/chromium/testing/local/GtestFilterTest.java",
     "javatests/src/org/chromium/testing/local/GtestLoggerTest.java",
     "javatests/src/org/chromium/testing/local/PackageFilterTest.java",
     "javatests/src/org/chromium/testing/local/RunnerFilterTest.java",
   ]
 }