Add a way to get the test data folder from junit.

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") {
   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",
     "java/src/org/chromium/testing/local/JsonLogger.java",
     "java/src/org/chromium/testing/local/JunitTestArgParser.java",
     "java/src/org/chromium/testing/local/JunitTestMain.java",
     "java/src/org/chromium/testing/local/GNManifestFactory.java",
     "java/src/org/chromium/testing/local/LocalRobolectricTestRunner.java",
     "java/src/org/chromium/testing/local/PackageFilter.java",
     "java/src/org/chromium/testing/local/RunnerFilter.java",
+    "java/src/org/chromium/testing/local/TestDir.java",
   ]
   deps = [
     "//third_party/junit",
     "//third_party/mockito:mockito_java",
     "//third_party/robolectric:robolectric_all_java",
   ]
 }
 
 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",
   ]
 }