Adds a first integration test for the Recent Tabs feature.

chrome/android/javatests/src/org/chromium/chrome/browser/offlinepages/RecentTabsTest.java

Index: chrome/android/javatests/src/org/chromium/chrome/browser/offlinepages/RecentTabsTest.java
diff --git a/chrome/android/javatests/src/org/chromium/chrome/browser/offlinepages/RecentTabsTest.java b/chrome/android/javatests/src/org/chromium/chrome/browser/offlinepages/RecentTabsTest.java
new file mode 100644
index 0000000000000000000000000000000000000000..30c10181b21a497d466b9c07e76aae26ba473327
--- /dev/null
+++ b/chrome/android/javatests/src/org/chromium/chrome/browser/offlinepages/RecentTabsTest.java
@@ -0,0 +1,152 @@
+// Copyright 2015 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.chrome.browser.offlinepages;
+
+import android.content.Context;
+import android.support.test.filters.MediumTest;
+
+import org.chromium.base.Callback;
+import org.chromium.base.ThreadUtils;
+import org.chromium.base.test.util.CommandLineFlags;
+import org.chromium.chrome.browser.offlinepages.OfflinePageBridge.OfflinePageModelObserver;
+import org.chromium.chrome.browser.profiles.Profile;
+import org.chromium.chrome.browser.tab.Tab;
+import org.chromium.chrome.test.ChromeTabbedActivityTestBase;
+import org.chromium.content.browser.test.util.Criteria;
+import org.chromium.content.browser.test.util.CriteriaHelper;
+import org.chromium.net.NetworkChangeNotifier;
+import org.chromium.net.test.EmbeddedTestServer;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.Semaphore;
+import java.util.concurrent.TimeUnit;
+
+/** Integration tests for the Last 1 feature of Offline Pages. */
+public class RecentTabsTest extends ChromeTabbedActivityTestBase {
+    private static final String TEST_PAGE = "/chrome/test/data/android/about.html";
+    private static final int TIMEOUT_MS = 5000;
+    private static final long POLLING_INTERVAL = 100;
+    private static final ClientId LAST_N_ID =

[carlosk, 2017/01/27 02:28:14]

Both POLLING_INTERVAL and LAST_N_ID are not being used.

[dewittj, 2017/01/30 17:32:37]

Done.

+            new ClientId(OfflinePageBridge.LAST_N_NAMESPACE, "1234");
+
+    private OfflinePageBridge mOfflinePageBridge;
+    private EmbeddedTestServer mTestServer;
+    private String mTestPage;
+
+    private void initializeBridgeForProfile(final boolean incognitoProfile)
+            throws InterruptedException {
+        final Semaphore semaphore = new Semaphore(0);
+        ThreadUtils.runOnUiThread(new Runnable() {
+            @Override
+            public void run() {
+                Profile profile = Profile.getLastUsedProfile();
+                if (incognitoProfile) {
+                    profile = profile.getOffTheRecordProfile();
+                }
+                // Ensure we start in an offline state.
+                mOfflinePageBridge = OfflinePageBridge.getForProfile(profile);
+                if (mOfflinePageBridge == null || mOfflinePageBridge.isOfflinePageModelLoaded()) {
+                    semaphore.release();
+                    return;
+                }
+                mOfflinePageBridge.addObserver(new OfflinePageModelObserver() {
+                    @Override
+                    public void offlinePageModelLoaded() {
+                        semaphore.release();
+                        mOfflinePageBridge.removeObserver(this);
+                    }
+                });
+            }
+        });
+        assertTrue(semaphore.tryAcquire(TIMEOUT_MS, TimeUnit.MILLISECONDS));
+    }
+
+    @Override
+    protected void setUp() throws Exception {
+        super.setUp();
+
+        ThreadUtils.runOnUiThreadBlocking(new Runnable() {
+            @Override
+            public void run() {
+                // Ensure we start in an offline state.
+                NetworkChangeNotifier.forceConnectivityState(false);
+                Context context = getActivity().getBaseContext();
+                if (!NetworkChangeNotifier.isInitialized()) {
+                    NetworkChangeNotifier.init(context);
+                }
+            }
+        });
+
+        initializeBridgeForProfile(false);
+
+        mTestServer = EmbeddedTestServer.createAndStartServer(getInstrumentation().getContext());
+        mTestPage = mTestServer.getURL(TEST_PAGE);
+    }
+
+    @Override
+    protected void tearDown() throws Exception {
+        mTestServer.stopAndDestroyServer();
+        super.tearDown();
+    }
+
+    @Override
+    public void startMainActivity() throws InterruptedException {
+        startMainActivityOnBlankPage();
+    }
+
+    @CommandLineFlags.Add({
+            "enable-features=OfflineRecentPages", "short-offline-page-snapshot-delay-for-test"})
+    @MediumTest

[fgorski, 2017/01/27 17:47:13]

https://developer.android.com/reference/android/support/test/filters/MediumTe...
vs.
https://developer.android.com/reference/android/support/test/filters/LargeTes...

[dewittj, 2017/01/30 17:32:37]

Now that sleep is removed, I think it should run in <1s so MediumTest is
appropriate.

+    public void testLastNPageSavedWhenTabSwitchedAfterLoadAndDelay() throws Exception {

[fgorski, 2017/01/27 17:47:13]

Can you add a bit of documentation to this test? (And simplify the name)

[dewittj, 2017/01/30 17:32:37]

Added more docs within the test, and simplified the name.

+        // The tab of interest.
+        final Tab tab = loadUrlInNewTab(mTestPage);
+        final ClientId clientId =
+                new ClientId(OfflinePageBridge.LAST_N_NAMESPACE, Integer.toString(tab.getId()));
+
+        // After load, with the testing flag we need to sleep a small amount to make sure that
+        // ShapshotController has a chance to fire StartSnapshot.
+        Thread.sleep(20);

[carlosk, 2017/01/27 02:28:14]

Sleeping in tests always makes me cringe but I don't see any way around it while
our own RMD strategy involves sleeping... :(

[Dmitry Titov, 2017/01/27 03:10:25]

Yes, is it possible to wait for a notification or observe something here?

[fgorski, 2017/01/27 17:47:13]

do we inform NTP of new last_n pages?

[dewittj, 2017/01/30 17:32:37]

To reply to everyone :)

The issue here was not to wait for a new offline page, I needed to wait until
SnapshotController believed it was in a good enough state to actually generate
an offline page /after/ switching tabs away.  I worked around this sleep by
making the delays in test 0ms, which means that the page will always be ready to
snapshot at the moment DomContentLoaded fires.  This test waits for onload,
which should always happen after DCL.

+
+        // Switch to a new tab to cause the hidden event.
+        loadUrlInNewTab(mTestPage);
+

[fgorski, 2017/01/27 17:47:13]

nit: You can probably move the clientId line here, as it will not be used until
this place.

[dewittj, 2017/01/30 17:32:37]

Acknowledged.

+        CriteriaHelper.pollInstrumentationThread(new Criteria() {
+            @Override
+            public boolean isSatisfied() {
+                try {
+                    return getPageByClientId(clientId) != null;
+                } catch (InterruptedException e) {
+                    return false;
+                }
+            }
+        });
+    }
+
+    private OfflinePageItem getPageByClientId(ClientId clientId) throws InterruptedException {
+        final OfflinePageItem[] result = {null};
+        final Semaphore semaphore = new Semaphore(0);
+        final List<ClientId> clientIdList = new ArrayList<>();
+        clientIdList.add(clientId);
+
+        ThreadUtils.runOnUiThread(new Runnable() {
+            @Override
+            public void run() {
+                mOfflinePageBridge.getPagesByClientIds(
+                        clientIdList, new Callback<List<OfflinePageItem>>() {
+                            @Override
+                            public void onResult(List<OfflinePageItem> items) {
+                                if (!items.isEmpty()) {
+                                    result[0] = items.get(0);
+                                }
+                                semaphore.release();
+                            }
+                        });
+            }
+        });
+        assertTrue(semaphore.tryAcquire(TIMEOUT_MS, TimeUnit.MILLISECONDS));
+        return result[0];
+    }
+}