weblayer: adds Tab.isDestroyed() and Browser.isDestroyed()

This way the embedder can readily detect when and if a Browser
or Tab has been destroyed.

BUG=1134085
TEST=covered by tests

Change-Id: I2e316e023d18c04d4aec6139306d1815e1ee65cb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2443402Reviewed-by: Evan Stade <estade@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#813009}

weblayer/browser/android/javatests/BUILD.gn

@@ -10,6 +10,7 @@ android_library("weblayer_java_tests") {
   testonly = true
   sources = [
     "src/org/chromium/weblayer/test/BrowserFragmentLifecycleTest.java",
+    "src/org/chromium/weblayer/test/BrowserTest.java",
     "src/org/chromium/weblayer/test/CookieManagerTest.java",
     "src/org/chromium/weblayer/test/CrashReporterTest.java",
     "src/org/chromium/weblayer/test/DataClearingTest.java",

weblayer/browser/android/javatests/src/org/chromium/weblayer/test/BrowserFragmentLifecycleTest.java

@@ -18,6 +18,7 @@ import org.junit.runner.RunWith;
 
 import org.chromium.base.test.util.CallbackHelper;
 import org.chromium.content_public.browser.test.util.TestThreadUtils;
+import org.chromium.weblayer.Browser;
 import org.chromium.weblayer.Navigation;
 import org.chromium.weblayer.NavigationCallback;
 import org.chromium.weblayer.NavigationController;
@@ -282,4 +283,25 @@ public class BrowserFragmentLifecycleTest {
         });
         helper.waitForCallback(callCount, 1);
     }
+
+    @Test
+    @SmallTest
+    public void browserAndTabIsDestroyedWhenFragmentDestroyed() throws Throwable {
+        mActivityTestRule.launchShellWithUrl(mActivityTestRule.getTestDataURL("simple_page.html"));
+
+        CallbackHelper helper = new CallbackHelper();
+        Browser browser = TestThreadUtils.runOnUiThreadBlocking(
+                () -> { return mActivityTestRule.getActivity().getBrowser(); });
+        Tab tab = TestThreadUtils.runOnUiThreadBlocking(() -> { return browser.getActiveTab(); });
+        TestThreadUtils.runOnUiThreadBlocking(() -> {
+            Assert.assertFalse(browser.isDestroyed());
+            Assert.assertFalse(tab.isDestroyed());
+            destroyFragment(helper);
+        });
+        helper.waitForFirst();
+        TestThreadUtils.runOnUiThreadBlocking(() -> {
+            Assert.assertTrue(browser.isDestroyed());
+            Assert.assertTrue(tab.isDestroyed());
+        });
+    }
 }

weblayer/browser/android/javatests/src/org/chromium/weblayer/test/BrowserTest.java

+// Copyright 2020 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.weblayer.test;
+
+import androidx.test.filters.SmallTest;
+
+import org.junit.Assert;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import org.chromium.content_public.browser.test.util.TestThreadUtils;
+import org.chromium.weblayer.Browser;
+import org.chromium.weblayer.Tab;
+import org.chromium.weblayer.shell.InstrumentationActivity;
+
+/**
+ * Tests for Browser.
+ */
+@RunWith(WebLayerJUnit4ClassRunner.class)
+public class BrowserTest {
+    @Rule
+    public InstrumentationActivityTestRule mActivityTestRule =
+            new InstrumentationActivityTestRule();
+
+    private InstrumentationActivity mActivity;
+
+    @Test
+    @SmallTest
+    public void testDestroyTab() {
+        String url = mActivityTestRule.getTestDataURL("before_unload.html");
+        mActivity = mActivityTestRule.launchShellWithUrl(url);
+        Assert.assertNotNull(mActivity);
+        TestThreadUtils.runOnUiThreadBlocking(() -> {
+            Browser browser = mActivity.getBrowser();
+            Tab tab = browser.getActiveTab();
+            Assert.assertFalse(tab.isDestroyed());
+            browser.destroyTab(tab);
+            Assert.assertTrue(tab.isDestroyed());
+        });
+    }
+}

weblayer/public/java/org/chromium/weblayer/Browser.java

@@ -73,6 +73,14 @@ public class Browser {
                                                    : null;
     }
 
+    /**
+     * Returns true if this Browser has been destroyed.
+     */
+    public boolean isDestroyed() {
+        ThreadCheck.ensureOnUiThread();
+        return mImpl == null;
+    }
+
     // Called prior to notifying IBrowser of destroy().
     void prepareForDestroy() {
         mFragment = null;

weblayer/public/java/org/chromium/weblayer/Tab.java

@@ -128,6 +128,14 @@ public class Tab {
         mBrowser = browser;
     }
 
+    /**
+     * Returns true if this Tab has been destroyed.
+     */
+    public boolean isDestroyed() {
+        ThreadCheck.ensureOnUiThread();
+        return mImpl == null;
+    }
+
     @NonNull
     public Browser getBrowser() {
         ThreadCheck.ensureOnUiThread();