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

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

Index: testing/android/junit/java/src/org/chromium/testing/local/TestDir.java
diff --git a/testing/android/junit/java/src/org/chromium/testing/local/TestDir.java b/testing/android/junit/java/src/org/chromium/testing/local/TestDir.java
new file mode 100644
index 0000000000000000000000000000000000000000..04ae55537f30c665a441e323d4009d53daab6433
--- /dev/null
+++ b/testing/android/junit/java/src/org/chromium/testing/local/TestDir.java
@@ -0,0 +1,26 @@
+// 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();
+    }
+}