Create a Junit 4 rule for running an EmbeddedTestServer.

It is a frequent pattern in tests to start an EmbeddedTestServer before
starting a test, and to stop it when the test completes. Simplify this
pattern by creating a Junit4 rule for running an EmbeddedTestServer.

Change-Id: Ibfdf4c032a0d223c674f09bf847998e62200a6f5
Reviewed-on: https://chromium-review.googlesource.com/548057Reviewed-by: Paweł Hajdan Jr. <phajdan.jr@chromium.org>
Reviewed-by: Helen Li <xunjieli@chromium.org>
Reviewed-by: Bernhard Bauer <bauerb@chromium.org>
Commit-Queue: Anthony Berent <aberent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#485306}

net/android/BUILD.gn

@@ -53,6 +53,7 @@ android_library("net_java_test_support") {
   testonly = true
   java_files = [
     "../test/android/javatests/src/org/chromium/net/test/EmbeddedTestServer.java",
+    "../test/android/javatests/src/org/chromium/net/test/EmbeddedTestServerRule.java",
     "../test/android/javatests/src/org/chromium/net/test/util/CertTestUtil.java",
     "../test/android/javatests/src/org/chromium/net/test/util/NetworkChangeNotifierTestUtil.java",
     "../test/android/javatests/src/org/chromium/net/test/util/TestWebServer.java",
@@ -62,6 +63,8 @@ android_library("net_java_test_support") {
     ":net_java",
     "//base:base_java",
     "//base:base_java_test_support",
+    "//third_party/android_support_test_runner:rules_java",
+    "//third_party/android_support_test_runner:runner_java",
     "//third_party/android_tools:android_support_annotations_java",
     "//third_party/junit",
   ]

net/test/android/javatests/src/org/chromium/net/test/EmbeddedTestServerRule.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.net.test;
+
+import android.support.test.InstrumentationRegistry;
+
+import org.junit.rules.TestWatcher;
+import org.junit.runner.Description;
+
+/**
+ * Junit4 rule for starting embedded test server before a test starts, and shutting it down when it
+ * finishes.
+ */
+public class EmbeddedTestServerRule extends TestWatcher {
+    EmbeddedTestServer mServer = new EmbeddedTestServer();
+
+    @Override
+    protected void starting(Description description) {
+        try {
+            EmbeddedTestServer.initializeAndStartServer(
+                    mServer, InstrumentationRegistry.getContext());
+        } catch (InterruptedException e) {
+            throw new EmbeddedTestServer.EmbeddedTestServerFailure("Test server didn't start");
+        }
+        super.starting(description);
+    }
+
+    @Override
+    protected void finished(Description description) {
+        super.finished(description);
+        mServer.stopAndDestroyServer();
+    }
+
+    /**
+     * Get the test server.
+     *
+     * @return the test server.
+     */
+    public EmbeddedTestServer getServer() {
+        return mServer;
+    }
+}