Reland "Cleanup XR usage of EmbeddedTestServer"

This is a reland of a8f4b170

No changes from original CL (erroneously reverted)

Original change's description:
> Cleanup XR usage of EmbeddedTestServer
>
> Cleans up manual usage of EmbeddedTestServer in XR tests, which was both
> adding a lot of duplicate code and had the potential to fail to clean up
> the server if the test failed, which could then affect other tests.
>
> This is achieved by making EmbeddedTestServerRule lazy and applying it
> to all ChromeActivityTestRules, not just WebappActivityTestRule.
>
> Bug: 901923
> Change-Id: I431dac3ce2488a1a5762a1ab1f5ec68aea16c9f5
> Reviewed-on: https://chromium-review.googlesource.com/c/1320024
> Commit-Queue: Brian Sheedy <bsheedy@chromium.org>
> Reviewed-by: Tommy Nyquist <nyquist@chromium.org>
> Reviewed-by: Paul Jensen <pauljensen@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#609556}

TBR=nyquist@chromium.org, pauljensen@chromium.org

Bug: 901923
Change-Id: I1d538672fc6b67d97a47f4bd165c4169e9b3f37c
Reviewed-on: https://chromium-review.googlesource.com/c/1344550Reviewed-by: Brian Sheedy <bsheedy@chromium.org>
Reviewed-by: Tommy Nyquist <nyquist@chromium.org>
Commit-Queue: Brian Sheedy <bsheedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609767}

chrome/android/javatests/src/org/chromium/chrome/browser/vr/VrBrowserDialogTest.java

@@ -13,10 +13,8 @@ import static org.chromium.chrome.test.util.ChromeRestriction.RESTRICTION_TYPE_V
 import android.graphics.Bitmap;
 import android.graphics.BitmapFactory;
 import android.graphics.PointF;
-import android.support.test.InstrumentationRegistry;
 import android.support.test.filters.LargeTest;
 
-import org.junit.After;
 import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Rule;
@@ -35,7 +33,6 @@ import org.chromium.chrome.browser.vr.util.VrBrowserTransitionUtils;
 import org.chromium.chrome.test.ChromeJUnit4ClassRunner;
 import org.chromium.chrome.test.util.RenderTestRule;
 import org.chromium.content_public.browser.test.util.JavaScriptUtils;
-import org.chromium.net.test.EmbeddedTestServer;
 
 import java.io.File;
 import java.io.IOException;
@@ -71,7 +68,6 @@ public class VrBrowserDialogTest {
             new RenderTestRule("components/test/data/permission_dialogs/render_tests");
 
     private VrBrowserTestFramework mVrBrowserTestFramework;
-    private EmbeddedTestServer mServer;
 
     @Before
     public void setUp() throws Exception {
@@ -81,13 +77,7 @@ public class VrBrowserDialogTest {
         if (!sBaseDirectory.exists() && !sBaseDirectory.isDirectory()) {
             Assert.assertTrue("Failed to make image capture directory", sBaseDirectory.mkdirs());
         }
-    }
-
-    @After
-    public void tearDown() throws Exception {
-        if (mServer != null) {
-            mServer.stopAndDestroyServer();
-        }
+        mVrTestRule.getEmbeddedTestServerRule().setServerPort(SERVER_PORT);
     }
 
     private void captureScreen(String filenameBase) throws InterruptedException {
@@ -115,12 +105,9 @@ public class VrBrowserDialogTest {
             throws InterruptedException, TimeoutException {
         // Trying to grant permissions on file:// URLs ends up hitting DCHECKS, so load from a local
         // server instead.
-        if (mServer == null) {
-            mServer = EmbeddedTestServer.createAndStartServerWithPort(
-                    InstrumentationRegistry.getContext(), SERVER_PORT);
-        }
         mVrBrowserTestFramework.loadUrlAndAwaitInitialization(
-                mServer.getURL(VrBrowserTestFramework.getEmbeddedServerPathForHtmlTestFile(page)),
+                mVrTestRule.getTestServer().getURL(
+                        VrBrowserTestFramework.getEmbeddedServerPathForHtmlTestFile(page)),
                 PAGE_LOAD_TIMEOUT_S);
 
         // Display the given permission prompt.

chrome/android/javatests/src/org/chromium/chrome/browser/vr/VrBrowserNativeUiTest.java

@@ -11,7 +11,6 @@ import static org.chromium.chrome.test.util.ChromeRestriction.RESTRICTION_TYPE_V
 
 import android.graphics.PointF;
 import android.os.SystemClock;
-import android.support.test.InstrumentationRegistry;
 import android.support.test.filters.MediumTest;
 
 import org.junit.Assert;
@@ -31,7 +30,6 @@ import org.chromium.chrome.browser.vr.util.VrBrowserTransitionUtils;
 import org.chromium.chrome.browser.vr.util.VrShellDelegateUtils;
 import org.chromium.chrome.test.ChromeJUnit4ClassRunner;
 import org.chromium.chrome.test.util.ChromeTabUtils;
-import org.chromium.net.test.EmbeddedTestServer;
 
 import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -93,11 +91,10 @@ public class VrBrowserNativeUiTest {
     @MediumTest
     public void testPaymentRequest() throws InterruptedException {
         // We can't request payment on file:// URLs, so use a local server.
-        EmbeddedTestServer server =
-                EmbeddedTestServer.createAndStartServer(InstrumentationRegistry.getContext());
         mVrBrowserTestFramework.loadUrlAndAwaitInitialization(
-                server.getURL(VrBrowserTestFramework.getEmbeddedServerPathForHtmlTestFile(
-                        "test_payment_request")),
+                mVrTestRule.getTestServer().getURL(
+                        VrBrowserTestFramework.getEmbeddedServerPathForHtmlTestFile(
+                                "test_payment_request")),
                 PAGE_LOAD_TIMEOUT_S);
         // Set up an observer so we'll know if the payment request is shown.
         AtomicBoolean requestShown = new AtomicBoolean(false);
@@ -124,7 +121,6 @@ public class VrBrowserNativeUiTest {
         Assert.assertTrue("Payment request caused VR exit",
                 VrShellDelegateUtils.getDelegateInstance().isVrEntryComplete());
         mVrBrowserTestFramework.endTest();
-        server.stopAndDestroyServer();
     }
 
     /**

chrome/android/javatests/src/org/chromium/chrome/browser/vr/VrBrowserTransitionTest.java

@@ -51,7 +51,6 @@ import org.chromium.chrome.test.util.ActivityUtils;
 import org.chromium.content_public.browser.test.util.CriteriaHelper;
 import org.chromium.content_public.browser.test.util.DOMUtils;
 import org.chromium.content_public.browser.test.util.JavaScriptUtils;
-import org.chromium.net.test.EmbeddedTestServer;
 
 import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -542,11 +541,10 @@ public class VrBrowserTransitionTest {
     @MediumTest
     public void testPermissionsPersistWhenEnteringVrBrowser() throws InterruptedException {
         // Permissions don't work on file:// URLs, so use a local server.
-        EmbeddedTestServer server =
-                EmbeddedTestServer.createAndStartServer(InstrumentationRegistry.getContext());
         mVrBrowserTestFramework.loadUrlAndAwaitInitialization(
-                server.getURL(VrBrowserTestFramework.getEmbeddedServerPathForHtmlTestFile(
-                        "test_permissions_persist_when_entering_vr_browser")),
+                mTestRule.getTestServer().getURL(
+                        VrBrowserTestFramework.getEmbeddedServerPathForHtmlTestFile(
+                                "test_permissions_persist_when_entering_vr_browser")),
                 PAGE_LOAD_TIMEOUT_S);
         // Ensure that permission requests initially trigger a prompt.
         Assert.assertTrue("Camera permission would not trigger prompt",
@@ -562,8 +560,9 @@ public class VrBrowserTransitionTest {
         mVrBrowserTestFramework.waitOnJavaScriptStep();
         // Reload the page and ensure that the permissions are still granted.
         mVrBrowserTestFramework.loadUrlAndAwaitInitialization(
-                server.getURL(VrBrowserTestFramework.getEmbeddedServerPathForHtmlTestFile(
-                        "test_permissions_persist_when_entering_vr_browser")),
+                mTestRule.getTestServer().getURL(
+                        VrBrowserTestFramework.getEmbeddedServerPathForHtmlTestFile(
+                                "test_permissions_persist_when_entering_vr_browser")),
                 PAGE_LOAD_TIMEOUT_S);
         Assert.assertFalse("Camera permission would trigger prompt after reload",
                 mVrBrowserTestFramework.permissionRequestWouldTriggerPrompt("camera"));
@@ -573,7 +572,6 @@ public class VrBrowserTransitionTest {
         VrBrowserTransitionUtils.forceEnterVrBrowserOrFail(POLL_TIMEOUT_LONG_MS);
         mVrBrowserTestFramework.executeStepAndWait("stepRequestPermission()");
         mVrBrowserTestFramework.endTest();
-        server.stopAndDestroyServer();
     }
 
     /**

chrome/android/javatests/src/org/chromium/chrome/browser/vr/WebXrArSessionTest.java

@@ -8,10 +8,8 @@ import static org.chromium.chrome.browser.vr.WebXrArTestFramework.PAGE_LOAD_TIME
 import static org.chromium.chrome.browser.vr.WebXrArTestFramework.POLL_TIMEOUT_LONG_MS;
 
 import android.os.Build;
-import android.support.test.InstrumentationRegistry;
 import android.support.test.filters.MediumTest;
 
-import org.junit.After;
 import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Rule;
@@ -30,7 +28,6 @@ import org.chromium.chrome.browser.vr.rules.XrActivityRestriction;
 import org.chromium.chrome.browser.vr.util.XrTestRuleUtils;
 import org.chromium.chrome.test.ChromeActivityTestRule;
 import org.chromium.chrome.test.ChromeJUnit4RunnerDelegate;
-import org.chromium.net.test.EmbeddedTestServer;
 
 import java.util.List;
 import java.util.concurrent.Callable;
@@ -52,9 +49,6 @@ public class WebXrArSessionTest {
 
     private ChromeActivityTestRule mTestRule;
     private WebXrArTestFramework mWebXrArTestFramework;
-    private EmbeddedTestServer mServer;
-
-    private boolean mShouldCreateServer;
 
     public WebXrArSessionTest(Callable<ChromeActivityTestRule> callable) throws Exception {
         mTestRule = callable.call();
@@ -64,21 +58,6 @@ public class WebXrArSessionTest {
     @Before
     public void setUp() throws Exception {
         mWebXrArTestFramework = new WebXrArTestFramework(mTestRule);
-        // WebappActivityTestRule automatically creates a test server, and creating multiple causes
-        // it to crash hitting a DCHECK. So, only handle the server ourselves if whatever test rule
-        // we're using doesn't create one itself.
-        mServer = mTestRule.getTestServer();
-        if (mServer == null) {
-            mShouldCreateServer = true;
-            mServer = EmbeddedTestServer.createAndStartServer(InstrumentationRegistry.getContext());
-        }
-    }
-
-    @After
-    public void tearDown() throws Exception {
-        if (mServer != null && mShouldCreateServer) {
-            mServer.stopAndDestroyServer();
-        }
     }
 
     /**
@@ -89,8 +68,9 @@ public class WebXrArSessionTest {
     @XrActivityRestriction({XrActivityRestriction.SupportedActivity.ALL})
     public void testArRequestSessionSucceeds() throws InterruptedException {
         mWebXrArTestFramework.loadUrlAndAwaitInitialization(
-                mServer.getURL(WebXrArTestFramework.getEmbeddedServerPathForHtmlTestFile(
-                        "test_ar_request_session_succeeds")),
+                mTestRule.getTestServer().getURL(
+                        WebXrArTestFramework.getEmbeddedServerPathForHtmlTestFile(
+                                "test_ar_request_session_succeeds")),
                 PAGE_LOAD_TIMEOUT_S);
         mWebXrArTestFramework.enterSessionWithUserGestureOrFail();
         mWebXrArTestFramework.assertNoJavaScriptErrors();
@@ -105,8 +85,9 @@ public class WebXrArSessionTest {
     @XrActivityRestriction({XrActivityRestriction.SupportedActivity.ALL})
     public void testRepeatedArSessionsSucceed() throws InterruptedException {
         mWebXrArTestFramework.loadUrlAndAwaitInitialization(
-                mServer.getURL(WebXrArTestFramework.getEmbeddedServerPathForHtmlTestFile(
-                        "test_ar_request_session_succeeds")),
+                mTestRule.getTestServer().getURL(
+                        WebXrArTestFramework.getEmbeddedServerPathForHtmlTestFile(
+                                "test_ar_request_session_succeeds")),
                 PAGE_LOAD_TIMEOUT_S);
         for (int i = 0; i < 2; i++) {
             mWebXrArTestFramework.enterSessionWithUserGestureOrFail();
@@ -124,8 +105,9 @@ public class WebXrArSessionTest {
     @XrActivityRestriction({XrActivityRestriction.SupportedActivity.ALL})
     public void testRepeatedArSessionsOnlyPromptPermissionsOnce() throws InterruptedException {
         mWebXrArTestFramework.loadUrlAndAwaitInitialization(
-                mServer.getURL(WebXrArTestFramework.getEmbeddedServerPathForHtmlTestFile(
-                        "test_ar_request_session_succeeds")),
+                mTestRule.getTestServer().getURL(
+                        WebXrArTestFramework.getEmbeddedServerPathForHtmlTestFile(
+                                "test_ar_request_session_succeeds")),
                 PAGE_LOAD_TIMEOUT_S);
         Assert.assertTrue("First AR session request did not trigger permission prompt",
                 mWebXrArTestFramework.permissionRequestWouldTriggerPrompt("camera"));

chrome/android/javatests/src/org/chromium/chrome/browser/vr/WebXrVrInputTest.java

@@ -15,7 +15,6 @@ import static org.chromium.chrome.test.util.ChromeRestriction.RESTRICTION_TYPE_V
 import android.graphics.PointF;
 import android.os.Build;
 import android.os.SystemClock;
-import android.support.test.InstrumentationRegistry;
 import android.support.test.filters.LargeTest;
 import android.support.test.filters.MediumTest;
 import android.view.MotionEvent;
@@ -52,7 +51,6 @@ import org.chromium.chrome.test.ChromeJUnit4RunnerDelegate;
 import org.chromium.content_public.browser.ViewEventSink;
 import org.chromium.content_public.browser.test.util.CriteriaHelper;
 import org.chromium.content_public.browser.test.util.TouchCommon;
-import org.chromium.net.test.EmbeddedTestServer;
 
 import java.util.List;
 import java.util.concurrent.Callable;
@@ -738,15 +736,10 @@ public class WebXrVrInputTest {
     private void testAppButtonLongPressDisplaysPermissionsImpl() throws InterruptedException {
         // Note that we need to pass in the WebContents to use throughout this because automatically
         // using the first tab's WebContents doesn't work in Incognito.
-        EmbeddedTestServer server = mTestRule.getTestServer();
-        boolean teardownServer = false;
-        if (server == null) {
-            server = EmbeddedTestServer.createAndStartServer(InstrumentationRegistry.getContext());
-            teardownServer = true;
-        }
         mWebXrVrTestFramework.loadUrlAndAwaitInitialization(
-                server.getURL(WebXrVrTestFramework.getEmbeddedServerPathForHtmlTestFile(
-                        "generic_webxr_permission_page")),
+                mTestRule.getTestServer().getURL(
+                        WebXrVrTestFramework.getEmbeddedServerPathForHtmlTestFile(
+                                "generic_webxr_permission_page")),
                 PAGE_LOAD_TIMEOUT_S);
         WebXrVrTestFramework.runJavaScriptOrFail("requestPermission({audio:true})",
                 POLL_TIMEOUT_SHORT_MS, mTestRule.getWebContents());
@@ -785,9 +778,6 @@ public class WebXrVrInputTest {
                 UserFriendlyElementName.WEB_XR_AUDIO_INDICATOR, true /* visible */, () -> {});
         NativeUiUtils.performActionAndWaitForVisibilityStatus(
                 UserFriendlyElementName.WEB_XR_AUDIO_INDICATOR, false /* visible */, () -> {});
-        if (teardownServer) {
-            server.stopAndDestroyServer();
-        }
     }
 
     /**
@@ -825,16 +815,10 @@ public class WebXrVrInputTest {
     private void testInSessionPermissionRequestsImpl() throws InterruptedException {
         // Note that we need to pass in the WebContents to use throughout this because automatically
         // using the first tab's WebContents doesn't work in Incognito.
-        EmbeddedTestServer server = mTestRule.getTestServer();
-        boolean teardownServer = false;
-        if (server == null) {
-            server = EmbeddedTestServer.createAndStartServer(InstrumentationRegistry.getContext());
-            teardownServer = true;
-        }
-
         mWebXrVrTestFramework.loadUrlAndAwaitInitialization(
-                server.getURL(WebXrVrTestFramework.getEmbeddedServerPathForHtmlTestFile(
-                        "generic_webxr_permission_page")),
+                mTestRule.getTestServer().getURL(
+                        WebXrVrTestFramework.getEmbeddedServerPathForHtmlTestFile(
+                                "generic_webxr_permission_page")),
                 PAGE_LOAD_TIMEOUT_S);
         mWebXrVrTestFramework.enterSessionWithUserGestureOrFail(mTestRule.getWebContents());
         NativeUiUtils.performActionAndWaitForVisibilityStatus(
@@ -861,9 +845,5 @@ public class WebXrVrInputTest {
                         .runJavaScriptOrFail("lastPermissionRequestSucceeded",
                                 POLL_TIMEOUT_SHORT_MS, mTestRule.getWebContents())
                         .equals("true"));
-
-        if (teardownServer) {
-            server.stopAndDestroyServer();
-        }
     }
 }

chrome/android/javatests/src/org/chromium/chrome/browser/vr/WebXrVrTabTest.java

@@ -9,7 +9,6 @@ import static org.chromium.chrome.browser.vr.XrTestFramework.POLL_TIMEOUT_SHORT_
 import static org.chromium.chrome.test.util.ChromeRestriction.RESTRICTION_TYPE_VIEWER_DAYDREAM_OR_STANDALONE;
 
 import android.os.Build;
-import android.support.test.InstrumentationRegistry;
 import android.support.test.filters.MediumTest;
 
 import org.junit.Before;
@@ -33,7 +32,6 @@ import org.chromium.chrome.browser.vr.util.PermissionUtils;
 import org.chromium.chrome.browser.vr.util.VrTestRuleUtils;
 import org.chromium.chrome.test.ChromeActivityTestRule;
 import org.chromium.chrome.test.ChromeJUnit4RunnerDelegate;
-import org.chromium.net.test.EmbeddedTestServer;
 
 import java.util.List;
 import java.util.concurrent.Callable;
@@ -128,16 +126,10 @@ public class WebXrVrTabTest {
     }
 
     private void testPermissionsInOtherTabImpl(boolean incognito) throws InterruptedException {
-        EmbeddedTestServer server = mTestRule.getTestServer();
-        boolean teardownServer = false;
-        if (server == null) {
-            server = EmbeddedTestServer.createAndStartServer(InstrumentationRegistry.getContext());
-            teardownServer = true;
-        }
-
         mWebXrVrTestFramework.loadUrlAndAwaitInitialization(
-                server.getURL(WebXrVrTestFramework.getEmbeddedServerPathForHtmlTestFile(
-                        "generic_webxr_permission_page")),
+                mTestRule.getTestServer().getURL(
+                        WebXrVrTestFramework.getEmbeddedServerPathForHtmlTestFile(
+                                "generic_webxr_permission_page")),
                 PAGE_LOAD_TIMEOUT_S);
         // Be sure to store the stream we're given so that the permission is actually in use, as
         // otherwise the toast doesn't show up since another tab isn't actually using the
@@ -165,9 +157,5 @@ public class WebXrVrTabTest {
         mWebXrVrTestFramework.enterSessionWithUserGestureOrFail(mTestRule.getWebContents());
         NativeUiUtils.performActionAndWaitForVisibilityStatus(
                 UserFriendlyElementName.WEB_XR_AUDIO_INDICATOR, true /* visible */, () -> {});
-
-        if (teardownServer) {
-            server.stopAndDestroyServer();
-        }
     }
 }

chrome/android/javatests/src/org/chromium/chrome/browser/webapps/WebappActivityTestRule.java

@@ -13,7 +13,6 @@ import android.support.test.InstrumentationRegistry;
 import android.view.ViewGroup;
 
 import org.junit.Assert;
-import org.junit.Rule;
 import org.junit.runner.Description;
 import org.junit.runners.model.Statement;
 
@@ -27,8 +26,6 @@ import org.chromium.content_public.browser.test.util.Criteria;
 import org.chromium.content_public.browser.test.util.CriteriaHelper;
 import org.chromium.content_public.browser.test.util.DOMUtils;
 import org.chromium.content_public.browser.test.util.JavaScriptUtils;
-import org.chromium.net.test.EmbeddedTestServer;
-import org.chromium.net.test.EmbeddedTestServerRule;
 
 /**
  * Custom {@link ChromeActivityTestRule} for tests using {@link WebappActivity}.
@@ -73,18 +70,10 @@ public class WebappActivityTestRule extends ChromeActivityTestRule<WebappActivit
             + "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
             + "AAAAAAAAAOA3AvAAAdln8YgAAAAASUVORK5CYII=";
 
-    @Rule
-    private EmbeddedTestServerRule mTestServerRule = new EmbeddedTestServerRule();
-
     public WebappActivityTestRule() {
         super(WebappActivity0.class);
     }
 
-    @Override
-    public EmbeddedTestServer getTestServer() {
-        return mTestServerRule.getServer();
-    }
-
     /**
      * Creates the Intent that starts the WebAppActivity. This is meant to be overriden by other
      * tests in order for them to pass some specific values, but it defaults to a web app that just
@@ -151,8 +140,7 @@ public class WebappActivityTestRule extends ChromeActivityTestRule<WebappActivit
             }
         };
 
-        Statement testServerStatement = mTestServerRule.apply(webappTestRuleStatement, description);
-        return super.apply(testServerStatement, description);
+        return super.apply(webappTestRuleStatement, description);
     }
 
     /**

chrome/test/android/javatests/src/org/chromium/chrome/test/ChromeActivityTestRule.java

@@ -19,6 +19,7 @@ import android.text.TextUtils;
 import android.view.Menu;
 
 import org.junit.Assert;
+import org.junit.Rule;
 import org.junit.runner.Description;
 import org.junit.runners.model.Statement;
 
@@ -60,6 +61,7 @@ import org.chromium.content_public.browser.test.util.CriteriaHelper;
 import org.chromium.content_public.browser.test.util.JavaScriptUtils;
 import org.chromium.content_public.browser.test.util.RenderProcessLimit;
 import org.chromium.net.test.EmbeddedTestServer;
+import org.chromium.net.test.EmbeddedTestServerRule;
 import org.chromium.ui.KeyboardVisibilityDelegate;
 import org.chromium.ui.base.PageTransition;
 
@@ -92,6 +94,9 @@ public class ChromeActivityTestRule<T extends ChromeActivity> extends ActivityTe
     private T mSetActivity;
     private String mCurrentTestName;
 
+    @Rule
+    private EmbeddedTestServerRule mTestServerRule = new EmbeddedTestServerRule();
+
     public ChromeActivityTestRule(Class<T> activityClass) {
         this(activityClass, false);
     }
@@ -104,7 +109,7 @@ public class ChromeActivityTestRule<T extends ChromeActivity> extends ActivityTe
     @Override
     public Statement apply(final Statement base, Description description) {
         mCurrentTestName = description.getMethodName();
-        final Statement superBase = super.apply(new Statement() {
+        Statement chromeActivityStatement = new Statement() {
             @Override
             public void evaluate() throws Throwable {
                 mDefaultUncaughtExceptionHandler = Thread.getDefaultUncaughtExceptionHandler();
@@ -123,8 +128,9 @@ public class ChromeActivityTestRule<T extends ChromeActivity> extends ActivityTe
 
                 base.evaluate();
             }
-        }, description);
-        return superBase;
+        };
+        Statement testServerStatement = mTestServerRule.apply(chromeActivityStatement, description);
+        return super.apply(testServerStatement, description);
     }
 
     /**
@@ -651,7 +657,14 @@ public class ChromeActivityTestRule<T extends ChromeActivity> extends ActivityTe
      * Gets the ChromeActivityTestRule's EmbeddedTestServer instance if it has one.
      */
     public EmbeddedTestServer getTestServer() {
-        return null;
+        return mTestServerRule.getServer();
+    }
+
+    /**
+     * Gets the underlying EmbeddedTestServerRule for getTestServer().
+     */
+    public EmbeddedTestServerRule getEmbeddedTestServerRule() {
+        return mTestServerRule;
     }
 
     /**

net/test/android/javatests/src/org/chromium/net/test/EmbeddedTestServerRule.java

@@ -9,39 +9,66 @@ import android.support.test.InstrumentationRegistry;
 import org.junit.rules.TestWatcher;
 import org.junit.runner.Description;
 
+import javax.annotation.concurrent.GuardedBy;
+
 /**
- * Junit4 rule for starting embedded test server before a test starts, and shutting it down when it
- * finishes.
+ * Junit4 rule for starting embedded test server when necessary (i.e. when accessed via
+ * {@link #getServer()}), and shutting it down when the test finishes.
  */
 public class EmbeddedTestServerRule extends TestWatcher {
-    EmbeddedTestServer mServer;
+    private final Object mLock = new Object();
+    @GuardedBy("mLock")
+    private EmbeddedTestServer mServer;
 
-    @Override
-    protected void starting(Description description) {
-        try {
-            mServer = EmbeddedTestServer.createAndStartServer(InstrumentationRegistry.getContext());
-        } catch (InterruptedException e) {
-            throw new EmbeddedTestServer.EmbeddedTestServerFailure("Test server didn't start");
-        }
-        super.starting(description);
-    }
+    // The default value of 0 will result in the same behavior as createAndStartServer
+    // (auto-selected port).
+    @GuardedBy("mLock")
+    private int mServerPort;
 
     @Override
     protected void finished(Description description) {
         super.finished(description);
-        mServer.stopAndDestroyServer();
+        synchronized (mLock) {
+            if (mServer != null) {
+                mServer.stopAndDestroyServer();
+            }
+        }
     }
 
     /**
-     * Get the test server.
+     * Get the test server, creating and starting it if it doesn't exist yet.
      *
      * @return the test server.
      */
     public EmbeddedTestServer getServer() {
-        return mServer;
+        synchronized (mLock) {
+            if (mServer == null) {
+                try {
+                    mServer = EmbeddedTestServer.createAndStartServerWithPort(
+                            InstrumentationRegistry.getContext(), mServerPort);
+                } catch (InterruptedException e) {
+                    throw new EmbeddedTestServer.EmbeddedTestServerFailure(
+                            "Test server didn't start");
+                }
+            }
+            return mServer;
+        }
     }
 
     public String getOrigin() {
-        return mServer.getURL("/");
+        return getServer().getURL("/");
+    }
+
+    /**
+     * Sets the port that the server will be started with. Must be called before the first
+     * {@link #getServer()} call.
+     *
+     * @param port the port to start the server with, or 0 for an automatically selected one.
+     */
+    public void setServerPort(int port) {
+        synchronized (mLock) {
+            assert mServer == null;
+            mServerPort = port;
+        }
     }
 }