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

BUG=

Review-Url: https://codereview.chromium.org/2788733002
Cr-Commit-Position: refs/heads/master@{#463328}

build/android/pylib/local/machine/local_machine_junit_test_run.py

@@ -28,9 +28,8 @@ class LocalMachineJunitTestRun(test_run.TestRun):
   #override
   def RunTests(self):
     with tempfile.NamedTemporaryFile() as json_file:
-      java_script = os.path.join(
-          constants.GetOutDirectory(), 'bin', 'helper',
-          self._test_instance.suite)
+      java_script = os.path.join(constants.GetOutDirectory(), 'bin', 'helper',
+                                 self._test_instance.suite)
       command = [java_script]
 
       # Add Jar arguments.
@@ -50,9 +49,11 @@ class LocalMachineJunitTestRun(test_run.TestRun):
       # TODO(mikecase): Add a --robolectric-dep-dir arg to test runner.
       # Have this arg set by GN in the generated test runner scripts.
       jvm_args += [
-          '-Drobolectric.dependency.dir=%s' %
-          os.path.join(constants.GetOutDirectory(),
-              'lib.java', 'third_party', 'robolectric')]
+          '-Drobolectric.dependency.dir=%s' % os.path.join(
+              constants.GetOutDirectory(), 'lib.java', 'third_party',
+              'robolectric'),
+          '-Ddir.source.root=%s' % constants.DIR_SOURCE_ROOT,
+      ]
       if self._test_instance.coverage_dir:
         if not os.path.exists(self._test_instance.coverage_dir):
           os.makedirs(self._test_instance.coverage_dir)

testing/android/junit/BUILD.gn

@@ -26,6 +26,7 @@ java_library("junit_test_support") {
     "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",

testing/android/junit/java/src/org/chromium/testing/local/TestDir.java

+// Copyright 2017 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.
+
+package org.chromium.testing.local;
+
+import java.io.File;
+
+/**
+ *  Tools to get the junit test path.
+ */
+public class TestDir {
+    private static final String TEST_FOLDER = "/chrome/test/data/";
+
+    /**
+     * Construct the full path of a test data file.
+     * @param path Pathname relative to chrome/test/data.
+     */
+    public static String getTestFilePath(String path) {
+        String junitRoot = System.getProperty("dir.source.root");
+        if (junitRoot == null) {
+            junitRoot = "";
+        }
+        return new File(junitRoot + TEST_FOLDER + path).getPath();
+    }
+}