Revert "Simplify ActivityTabProvider implementation"

This reverts commit 54ff0ea1.

Original patch created a problem around properly switching themes,
because of timing of switching observer to a new tab (previously
available with a hint only.

Bug: 1056586, 1054072
Change-Id: Iec9267e6eadd87725bf4609117b8d4d31a2fd24e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2080692
Commit-Queue: Filip Gorski <fgorski@chromium.org>
Reviewed-by: Matthew Jones <mdjones@chromium.org>
Reviewed-by: David Trainor <dtrainor@chromium.org>
Cr-Commit-Position: refs/heads/master@{#746038}

chrome/android/features/autofill_assistant/public/java/src/org/chromium/chrome/browser/autofill_assistant/AutofillAssistantFacade.java

@@ -13,6 +13,7 @@ import androidx.annotation.Nullable;
 import org.chromium.base.BuildInfo;
 import org.chromium.base.Callback;
 import org.chromium.base.IntentUtils;
+import org.chromium.chrome.browser.ActivityTabProvider;
 import org.chromium.chrome.browser.ChromeActivity;
 import org.chromium.chrome.browser.autofill_assistant.metrics.DropOutReason;
 import org.chromium.chrome.browser.directactions.DirectActionHandler;
@@ -207,9 +208,10 @@ public class AutofillAssistantFacade {
         }
 
         // The tab is not yet available. We need to register as listener and wait for it.
-        activity.getActivityTabProvider().addObserver(new Callback<Tab>() {
+        activity.getActivityTabProvider().addObserverAndTrigger(
+                new ActivityTabProvider.HintlessActivityTabObserver() {
                     @Override
-            public void onResult(Tab tab) {
+                    public void onActivityTabChanged(Tab tab) {
                         if (tab == null) return;
                         activity.getActivityTabProvider().removeObserver(this);
                         assert tab.getWebContents() != null;

chrome/android/features/keyboard_accessory/junit/src/org/chromium/chrome/browser/keyboard_accessory/ManualFillingControllerTest.java

@@ -132,7 +132,6 @@ public class ManualFillingControllerTest {
     private static class MockActivityTabProvider extends ActivityTabProvider {
         public Tab mTab;
 
-        @Override
         public void set(Tab tab) {
             mTab = tab;
         }

chrome/android/java/src/org/chromium/chrome/browser/ActivityTabProvider.java

@@ -7,8 +7,9 @@ package org.chromium.chrome.browser;
 import androidx.annotation.CallSuper;
 import androidx.annotation.VisibleForTesting;
 
-import org.chromium.base.Callback;
-import org.chromium.base.supplier.ObservableSupplierImpl;
+import org.chromium.base.ObserverList;
+import org.chromium.base.ObserverList.RewindableIterator;
+import org.chromium.base.supplier.Supplier;
 import org.chromium.chrome.browser.compositor.layouts.Layout;
 import org.chromium.chrome.browser.compositor.layouts.LayoutManager;
 import org.chromium.chrome.browser.compositor.layouts.SceneChangeObserver;
@@ -17,13 +18,44 @@ import org.chromium.chrome.browser.compositor.layouts.phone.SimpleAnimationLayou
 import org.chromium.chrome.browser.tab.EmptyTabObserver;
 import org.chromium.chrome.browser.tab.Tab;
 import org.chromium.chrome.browser.tab.TabSelectionType;
+import org.chromium.chrome.browser.tabmodel.TabModel;
 import org.chromium.chrome.browser.tabmodel.TabModelSelector;
 import org.chromium.chrome.browser.tabmodel.TabModelSelectorTabModelObserver;
 
 /**
  * A class that provides the current {@link Tab} for various states of the browser's activity.
  */
-public class ActivityTabProvider extends ObservableSupplierImpl<Tab> {
+public class ActivityTabProvider implements Supplier<Tab> {
+    /** An interface to track the visible tab for the activity. */
+    public interface ActivityTabObserver {
+        /**
+         * A notification that the activity's tab has changed. This will be triggered whenever a
+         * different tab is selected by the active {@link TabModel} and when that tab is
+         * interactive (i.e. not in a tab switching mode). When switching to toolbar swipe or tab
+         * switcher, this method will be called with {@code null} to indicate that there is no
+         * single activity tab (observers may or may not choose to ignore this event).
+         * @param tab The {@link Tab} that became visible or null if not in {@link StaticLayout}.
+         * @param hint Whether the change event is a hint that a tab change is likely. If true, the
+         *             provided tab may still be frozen and is not yet selected.
+         */
+        void onActivityTabChanged(Tab tab, boolean hint);
+    }
+
+    /** An {@link ActivityTabObserver} that can be used to explicitly watch non-hint events. */
+    public abstract static class HintlessActivityTabObserver implements ActivityTabObserver {
+        @Override
+        public final void onActivityTabChanged(Tab tab, boolean hint) {
+            // Only pass the event through if it isn't a hint.
+            if (!hint) onActivityTabChanged(tab);
+        }
+
+        /**
+         * A notification that the {@link Tab} in the {@link StaticLayout} has changed.
+         * @param tab The activity's tab.
+         */
+        public abstract void onActivityTabChanged(Tab tab);
+    }
+
     /**
      * A utility class for observing the activity tab via {@link TabObserver}. When the activity
      * tab changes, the observer is switched to that tab.
@@ -33,7 +65,7 @@ public class ActivityTabProvider extends ObservableSupplierImpl<Tab> {
         private final ActivityTabProvider mTabProvider;
 
         /** An observer to watch for a changing activity tab and move this tab observer. */
-        private final Callback<Tab> mActivityTabObserver;
+        private final ActivityTabObserver mActivityTabObserver;
 
         /** The current activity tab. */
         private Tab mTab;
@@ -44,12 +76,12 @@ public class ActivityTabProvider extends ObservableSupplierImpl<Tab> {
          */
         public ActivityTabTabObserver(ActivityTabProvider tabProvider) {
             mTabProvider = tabProvider;
-            mActivityTabObserver = (tab) -> {
+            mActivityTabObserver = (tab, hint) -> {
                 updateObservedTab(tab);
                 onObservingDifferentTab(tab);
             };
-            addObserverToTabProvider();
-            updateObservedTabToCurrent();
+            mTabProvider.addObserver(mActivityTabObserver);
+            updateObservedTab(mTabProvider.get());
         }
 
         /**
@@ -78,24 +110,21 @@ public class ActivityTabProvider extends ObservableSupplierImpl<Tab> {
                 mTab.removeObserver(this);
                 mTab = null;
             }
-            removeObserverFromTabProvider();
+            mTabProvider.removeObserver(mActivityTabObserver);
         }
-
-        @VisibleForTesting
-        protected void updateObservedTabToCurrent() {
-            updateObservedTab(mTabProvider.get());
     }
 
-        @VisibleForTesting
-        protected void addObserverToTabProvider() {
-            mTabProvider.addObserver(mActivityTabObserver);
-        }
+    /** The list of observers to send events to. */
+    private final ObserverList<ActivityTabObserver> mObservers = new ObserverList<>();
 
-        @VisibleForTesting
-        protected void removeObserverFromTabProvider() {
-            mTabProvider.removeObserver(mActivityTabObserver);
-        }
-    }
+    /**
+     * A single rewindable iterator bound to {@link #mObservers} to prevent constant allocation of
+     * new iterators.
+     */
+    private final RewindableIterator<ActivityTabObserver> mRewindableIterator;
+
+    /** The {@link Tab} that is considered to be the activity's tab. */
+    private Tab mActivityTab;
 
     /** A handle to the {@link LayoutManager} to get the active layout. */
     private LayoutManager mLayoutManager;
@@ -109,11 +138,25 @@ public class ActivityTabProvider extends ObservableSupplierImpl<Tab> {
     /** An observer for watching tab creation and switching events. */
     private TabModelSelectorTabModelObserver mTabModelObserver;
 
-    /** Default constructor. */
+    /** The last tab ID that was hinted. This is reset when the activity tab actually changes. */
+    private int mLastHintedTabId;
+
+    /**
+     * Default constructor.
+     */
     public ActivityTabProvider() {
+        mRewindableIterator = mObservers.rewindableIterator();
         mSceneChangeObserver = new SceneChangeObserver() {
             @Override
-            public void onTabSelectionHinted(int tabId) {}
+            public void onTabSelectionHinted(int tabId) {
+                if (mTabModelSelector == null || mLastHintedTabId == tabId) return;
+                Tab tab = mTabModelSelector.getTabById(tabId);
+                mLastHintedTabId = tabId;
+                mRewindableIterator.rewind();
+                while (mRewindableIterator.hasNext()) {
+                    mRewindableIterator.next().onActivityTabChanged(tab, true);
+                }
+            }
 
             @Override
             public void onSceneChange(Layout layout) {
@@ -130,6 +173,14 @@ public class ActivityTabProvider extends ObservableSupplierImpl<Tab> {
         };
     }
 
+    /**
+     * @return The activity's current tab.
+     */
+    @Override
+    public Tab get() {
+        return mActivityTab;
+    }
+
     /**
      * @param selector A {@link TabModelSelector} for watching for changes in tabs.
      */
@@ -172,11 +223,50 @@ public class ActivityTabProvider extends ObservableSupplierImpl<Tab> {
             return;
         }
 
-        set(tab);
+        if (mActivityTab == tab) return;
+        mActivityTab = tab;
+        mLastHintedTabId = Tab.INVALID_TAB_ID;
+
+        mRewindableIterator.rewind();
+        while (mRewindableIterator.hasNext()) {
+            mRewindableIterator.next().onActivityTabChanged(tab, false);
+        }
+    }
+
+    /**
+     * Add an observer but do not immediately trigger the event. This should only be used in
+     * extremely specific cases where the observer would trigger an event from the constructor of
+     * the implementing class (see {@link ActivityTabTabObserver}).
+     * @param observer The observer to be added.
+     *
+     * TODO(fgorski): Find a different way to mock this in tests for {@link LoadProgressMediator}.
+     */
+    @VisibleForTesting
+    @Deprecated
+    public void addObserver(ActivityTabObserver observer) {
+        mObservers.addObserver(observer);
+    }
+
+    /**
+     * @param observer The {@link ActivityTabObserver} to add to the activity. This will trigger the
+     *                 {@link ActivityTabObserver#onActivityTabChanged(Tab, boolean)} event to be
+     *                 called on the added observer, providing access to the current tab.
+     */
+    public void addObserverAndTrigger(ActivityTabObserver observer) {
+        mObservers.addObserver(observer);
+        observer.onActivityTabChanged(mActivityTab, false);
+    }
+
+    /**
+     * @param observer The {@link ActivityTabObserver} to remove from the activity.
+     */
+    public void removeObserver(ActivityTabObserver observer) {
+        mObservers.removeObserver(observer);
     }
 
     /** Clean up and detach any observers this object created. */
     public void destroy() {
+        mObservers.clear();
         if (mLayoutManager != null) mLayoutManager.removeSceneChangeObserver(mSceneChangeObserver);
         mLayoutManager = null;
         if (mTabModelObserver != null) mTabModelObserver.destroy();

chrome/android/java/src/org/chromium/chrome/browser/customtabs/content/CustomTabActivityTabController.java

@@ -18,6 +18,7 @@ import androidx.browser.trusted.sharing.ShareTarget;
 import org.chromium.base.IntentUtils;
 import org.chromium.base.metrics.RecordHistogram;
 import org.chromium.chrome.browser.ActivityTabProvider;
+import org.chromium.chrome.browser.ActivityTabProvider.HintlessActivityTabObserver;
 import org.chromium.chrome.browser.ChromeActivity;
 import org.chromium.chrome.browser.IntentHandler;
 import org.chromium.chrome.browser.ServiceTabLauncher;
@@ -105,6 +106,14 @@ public class CustomTabActivityTabController
     private final CustomTabsSessionToken mSession;
     private final Intent mIntent;
 
+    @Nullable
+    private HintlessActivityTabObserver mTabSwapObserver = new HintlessActivityTabObserver() {
+        @Override
+        public void onActivityTabChanged(@Nullable Tab tab) {
+            mTabProvider.swapTab(tab);
+        }
+    };
+
     @Inject
     public CustomTabActivityTabController(ChromeActivity<?> activity,
             Lazy<CustomTabDelegateFactory> customTabDelegateFactory,
@@ -328,7 +337,7 @@ public class CustomTabActivityTabController
         } // else we've already set the initial tab.
 
         // Listen to tab swapping and closing.
-        mActivityTabProvider.addObserver(mTabProvider::swapTab);
+        mActivityTabProvider.addObserverAndTrigger(mTabSwapObserver);
     }
 
     @Nullable

chrome/android/java/src/org/chromium/chrome/browser/toolbar/bottom/BrowsingModeBottomToolbarCoordinator.java

@@ -12,6 +12,7 @@ import org.chromium.base.Callback;
 import org.chromium.base.supplier.ObservableSupplier;
 import org.chromium.chrome.R;
 import org.chromium.chrome.browser.ActivityTabProvider;
+import org.chromium.chrome.browser.ActivityTabProvider.HintlessActivityTabObserver;
 import org.chromium.chrome.browser.ThemeColorProvider;
 import org.chromium.chrome.browser.compositor.layouts.OverviewModeBehavior;
 import org.chromium.chrome.browser.feature_engagement.TrackerFactory;
@@ -140,9 +141,9 @@ public class BrowsingModeBottomToolbarCoordinator {
      *         TabSwitcherButtonView} just passes null.
      */
     void setupIPH(@FeatureConstants String feature, View anchor, OnClickListener listener) {
-        mTabProvider.addObserver(new Callback<Tab>() {
+        mTabProvider.addObserverAndTrigger(new HintlessActivityTabObserver() {
             @Override
-            public void onResult(Tab tab) {
+            public void onActivityTabChanged(Tab tab) {
                 if (tab == null) return;
                 TabImpl tabImpl = (TabImpl) tab;
                 final Tracker tracker = TrackerFactory.getTrackerForProfile(tabImpl.getProfile());

chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappActivityTabController.java

@@ -10,6 +10,7 @@ import android.os.Bundle;
 import androidx.annotation.Nullable;
 
 import org.chromium.chrome.browser.ActivityTabProvider;
+import org.chromium.chrome.browser.ActivityTabProvider.HintlessActivityTabObserver;
 import org.chromium.chrome.browser.ChromeActivity;
 import org.chromium.chrome.browser.WebContentsFactory;
 import org.chromium.chrome.browser.browserservices.BrowserServicesActivityTabController;
@@ -45,6 +46,13 @@ public class WebappActivityTabController implements BrowserServicesActivityTabCo
     private final WebContentsFactory mWebContentsFactory;
     private final CustomTabActivityTabProvider mTabProvider;
 
+    private HintlessActivityTabObserver mTabSwapObserver = new HintlessActivityTabObserver() {
+        @Override
+        public void onActivityTabChanged(@Nullable Tab tab) {
+            mTabProvider.swapTab(tab);
+        }
+    };
+
     @Inject
     public WebappActivityTabController(ChromeActivity<?> activity,
             Lazy<CustomTabDelegateFactory> tabDelegateFactory,
@@ -131,7 +139,7 @@ public class WebappActivityTabController implements BrowserServicesActivityTabCo
         mTabProvider.setInitialTab(tab, mode);
 
         // Listen to tab swapping and closing.
-        mActivityTabProvider.addObserver(mTabProvider::swapTab);
+        mActivityTabProvider.addObserverAndTrigger(mTabSwapObserver);
     }
 
     @Nullable

chrome/android/java/src/org/chromium/chrome/browser/widget/bottomsheet/BottomSheetController.java

@@ -12,6 +12,7 @@ import androidx.annotation.VisibleForTesting;
 
 import org.chromium.base.supplier.Supplier;
 import org.chromium.chrome.browser.ActivityTabProvider;
+import org.chromium.chrome.browser.ActivityTabProvider.HintlessActivityTabObserver;
 import org.chromium.chrome.browser.compositor.bottombar.OverlayPanel;
 import org.chromium.chrome.browser.compositor.bottombar.OverlayPanelManager;
 import org.chromium.chrome.browser.fullscreen.ChromeFullscreenManager;
@@ -134,9 +135,6 @@ public class BottomSheetController implements Destroyable {
     /** The last known activity tab, if available. */
     private Tab mLastActivityTab;
 
-    /** A tab observer to watch the last known activity tab. */
-    private TabObserver mTabObserver;
-
     /** A runnable that initializes the bottom sheet when necessary. */
     private Runnable mSheetInitializer;
 
@@ -256,7 +254,7 @@ public class BottomSheetController implements Destroyable {
 
         VrModuleProvider.registerVrModeObserver(mVrModeObserver);
 
-        mTabObserver = new EmptyTabObserver() {
+        final TabObserver tabObserver = new EmptyTabObserver() {
             @Override
             public void onPageLoadStarted(Tab tab, String url) {
                 clearRequestsAndHide();
@@ -278,8 +276,29 @@ public class BottomSheetController implements Destroyable {
             }
         };
 
-        mTabProvider.addObserver(this::setActivityTab);
-        setActivityTab(mTabProvider.get());
+        mTabProvider.addObserverAndTrigger(new HintlessActivityTabObserver() {
+            @Override
+            public void onActivityTabChanged(Tab tab) {
+                // Temporarily suppress the sheet if entering a state where there is no activity
+                // tab.
+                if (tab == null) {
+                    suppressSheet(StateChangeReason.COMPOSITED_UI);
+                    return;
+                }
+
+                // If refocusing the same tab, simply unsuppress the sheet.
+                if (mLastActivityTab == tab) {
+                    unsuppressSheet();
+                    return;
+                }
+
+                // Move the observer to the new activity tab and clear the sheet.
+                if (mLastActivityTab != null) mLastActivityTab.removeObserver(tabObserver);
+                mLastActivityTab = tab;
+                mLastActivityTab.addObserver(tabObserver);
+                clearRequestsAndHide();
+            }
+        });
 
         ScrimObserver scrimObserver = new ScrimObserver() {
             @Override
@@ -346,26 +365,6 @@ public class BottomSheetController implements Destroyable {
         mSheetInitializer = null;
     }
 
-    private void setActivityTab(Tab tab) {
-        // Temporarily suppress the sheet if entering a state where there is no activity tab.
-        if (tab == null) {
-            suppressSheet(StateChangeReason.COMPOSITED_UI);
-            return;
-        }
-
-        // If refocusing the same tab, simply unsuppress the sheet.
-        if (mLastActivityTab == tab) {
-            unsuppressSheet();
-            return;
-        }
-
-        // Move the observer to the new activity tab and clear the sheet.
-        if (mLastActivityTab != null) mLastActivityTab.removeObserver(mTabObserver);
-        mLastActivityTab = tab;
-        mLastActivityTab.addObserver(mTabObserver);
-        clearRequestsAndHide();
-    }
-
     /**
      * Create a ScrimParams anchoring on the bottom-sheet view.
      * @param scrimObserver The scrimObserver to set for the ScrimParams.

chrome/android/javatests/src/org/chromium/chrome/browser/ActivityTabProviderTest.java

@@ -8,6 +8,7 @@ import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotEquals;
 
 import android.support.test.InstrumentationRegistry;
+import android.support.test.filters.LargeTest;
 import android.support.test.filters.SmallTest;
 
 import org.junit.Before;
@@ -41,32 +42,22 @@ import java.util.concurrent.TimeoutException;
 public class ActivityTabProviderTest {
     /** A test observer that provides access to the tab being observed. */
     private static class TestActivityTabTabObserver extends ActivityTabTabObserver {
+        /** Callback helper for notification that the observer is watching a different tab. */
+        private CallbackHelper mObserverMoveHelper;
+
         /** The tab currently being observed. */
         private Tab mObservedTab;
 
         public TestActivityTabTabObserver(ActivityTabProvider provider) {
             super(provider);
-            TestThreadUtils.runOnUiThreadBlockingNoException(() -> mObservedTab = provider.get());
+            mObserverMoveHelper = new CallbackHelper();
+            mObservedTab = provider.get();
         }
 
         @Override
         public void onObservingDifferentTab(Tab tab) {
             mObservedTab = tab;
-        }
-
-        @Override
-        protected void updateObservedTabToCurrent() {
-            TestThreadUtils.runOnUiThreadBlocking(super::updateObservedTabToCurrent);
-        }
-
-        @Override
-        protected void addObserverToTabProvider() {
-            TestThreadUtils.runOnUiThreadBlocking(super::addObserverToTabProvider);
-        }
-
-        @Override
-        protected void removeObserverFromTabProvider() {
-            TestThreadUtils.runOnUiThreadBlocking(super::removeObserverFromTabProvider);
+            mObserverMoveHelper.notifyCalled();
         }
     }
 
@@ -77,21 +68,23 @@ public class ActivityTabProviderTest {
     private ActivityTabProvider mProvider;
     private Tab mActivityTab;
     private CallbackHelper mActivityTabChangedHelper = new CallbackHelper();
+    private CallbackHelper mActivityTabChangedHintHelper = new CallbackHelper();
 
     @Before
     public void setUp() throws Exception {
         mActivityTestRule.startMainActivityOnBlankPage();
-        TestThreadUtils.runOnUiThreadBlocking(() -> {
         mActivity = mActivityTestRule.getActivity();
         mProvider = mActivity.getActivityTabProvider();
-            mProvider.addObserver(tab -> {
+        mProvider.addObserverAndTrigger((tab, hint) -> {
+            if (hint) {
+                mActivityTabChangedHintHelper.notifyCalled();
+            } else {
                 mActivityTab = tab;
                 mActivityTabChangedHelper.notifyCalled();
+            }
         });
-        });
-        mActivityTabChangedHelper.waitForCallback(0);
-        assertEquals("Setup should have only triggered the event once.", 1,
-                mActivityTabChangedHelper.getCallCount());
+        assertEquals("Setup should have only triggered the event once.",
+                mActivityTabChangedHelper.getCallCount(), 1);
     }
 
     /**
@@ -110,8 +103,7 @@ public class ActivityTabProviderTest {
     @Feature({"ActivityTabObserver"})
     public void testTriggerOnAddObserver() throws TimeoutException {
         CallbackHelper helper = new CallbackHelper();
-        TestThreadUtils.runOnUiThreadBlocking(
-                () -> { mProvider.addObserver(tab -> helper.notifyCalled()); });
+        mProvider.addObserverAndTrigger((tab, hint) -> helper.notifyCalled());
         helper.waitForCallback(0);
 
         assertEquals("Only the added observer should have been triggered.",
@@ -145,6 +137,27 @@ public class ActivityTabProviderTest {
                 mActivityTab);
     }
 
+    /** Test that the hint event triggers when exiting the tab switcher. */
+    @Test
+    @LargeTest
+    @Feature({"ActivityTabObserver"})
+    @Restriction(UiRestriction.RESTRICTION_TYPE_PHONE)
+    public void testTriggerHintWithTabSwitcher() throws TimeoutException {
+        assertEquals("The hint should not yet have triggered.", 0,
+                mActivityTabChangedHintHelper.getCallCount());
+
+        setTabSwitcherModeAndWait(true);
+
+        assertEquals("The hint should not yet have triggered.", 0,
+                mActivityTabChangedHintHelper.getCallCount());
+
+        setTabSwitcherModeAndWait(false);
+        mActivityTabChangedHintHelper.waitForCallback(0);
+
+        assertEquals("The hint should have triggerd once.", 1,
+                mActivityTabChangedHintHelper.getCallCount());
+    }
+
     /**
      * Test that onActivityTabChanged is triggered when switching to a new tab without switching
      * layouts.
@@ -220,7 +233,7 @@ public class ActivityTabProviderTest {
     @Test
     @SmallTest
     @Feature({"ActivityTabObserver"})
-    public void testActivityTabTabObserver() throws TimeoutException {
+    public void testActivityTabTabObserver() {
         Tab startingTab = getModelSelectedTab();
 
         TestActivityTabTabObserver tabObserver = new TestActivityTabTabObserver(mProvider);

chrome/android/javatests/src/org/chromium/chrome/browser/gesturenav/NavigationHandlerTest.java

@@ -32,7 +32,6 @@ import org.chromium.chrome.test.util.ChromeTabUtils;
 import org.chromium.components.embedder_support.util.UrlConstants;
 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.TestThreadUtils;
 import org.chromium.content_public.browser.test.util.TouchCommon;
 import org.chromium.content_public.common.ContentUrlConstants;
 import org.chromium.net.test.EmbeddedTestServer;
@@ -71,8 +70,7 @@ public class NavigationHandlerTest {
     }
 
     private Tab currentTab() {
-        return TestThreadUtils.runOnUiThreadBlockingNoException(
-                () -> mActivityTestRule.getActivity().getActivityTabProvider().get());
+        return mActivityTestRule.getActivity().getActivityTabProvider().get();
     }
 
     private void loadNewTabPage() {

chrome/android/javatests/src/org/chromium/chrome/browser/widget/bottomsheet/BottomSheetControllerTest.java

@@ -98,13 +98,7 @@ public class BottomSheetControllerTest {
 
     /** @return The height of the container view. */
     private int getContainerHeight() {
-        return TestThreadUtils.runOnUiThreadBlockingNoException(
-                ()
-                        -> mActivityTestRule.getActivity()
-                                   .getActivityTabProvider()
-                                   .get()
-                                   .getView()
-                                   .getHeight());
+        return mActivityTestRule.getActivity().getActivityTabProvider().get().getView().getHeight();
     }
 
     @Test

chrome/android/junit/src/org/chromium/chrome/browser/customtabs/content/CustomTabActivityContentTestEnvironment.java

@@ -8,6 +8,7 @@ import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyBoolean;
 import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.doNothing;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
@@ -24,11 +25,11 @@ import org.mockito.Captor;
 import org.mockito.Mock;
 import org.mockito.MockitoAnnotations;
 
-import org.chromium.base.Callback;
 import org.chromium.base.UserDataHost;
 import org.chromium.base.metrics.RecordHistogram;
 import org.chromium.base.metrics.RecordUserAction;
 import org.chromium.chrome.browser.ActivityTabProvider;
+import org.chromium.chrome.browser.ActivityTabProvider.ActivityTabObserver;
 import org.chromium.chrome.browser.ChromeActivity;
 import org.chromium.chrome.browser.IntentHandler;
 import org.chromium.chrome.browser.WarmupManager;
@@ -100,7 +101,7 @@ public class CustomTabActivityContentTestEnvironment extends TestWatcher {
     public final CustomTabActivityTabProvider tabProvider = new CustomTabActivityTabProvider();
 
     @Captor
-    public ArgumentCaptor<Callback<Tab>> activityTabObserverCaptor;
+    public ArgumentCaptor<ActivityTabObserver> activityTabObserverCaptor;
 
     // Captures the WebContents with which tabFromFactory is initialized
     @Captor public ArgumentCaptor<WebContents> webContentsCaptor;
@@ -128,7 +129,9 @@ public class CustomTabActivityContentTestEnvironment extends TestWatcher {
 
         when(startupTabPreloader.takeTabIfMatchingOrDestroy(any(), anyInt())).thenReturn(null);
         when(reparentingTaskProvider.get(any())).thenReturn(reparentingTask);
-        when(activityTabProvider.addObserver(activityTabObserverCaptor.capture())).thenReturn(null);
+        doNothing()
+                .when(activityTabProvider)
+                .addObserverAndTrigger(activityTabObserverCaptor.capture());
     }
 
     @Override
@@ -178,8 +181,8 @@ public class CustomTabActivityContentTestEnvironment extends TestWatcher {
 
     public void changeTab(Tab newTab) {
         when(activityTabProvider.get()).thenReturn(newTab);
-        for (Callback<Tab> observer : activityTabObserverCaptor.getAllValues()) {
-            observer.onResult(newTab);
+        for (ActivityTabObserver observer : activityTabObserverCaptor.getAllValues()) {
+            observer.onActivityTabChanged(newTab, false);
         }
     }
 

chrome/android/junit/src/org/chromium/chrome/browser/toolbar/load_progress/LoadProgressMediatorTest.java

@@ -23,11 +23,10 @@ import org.mockito.MockitoAnnotations;
 import org.robolectric.Shadows;
 import org.robolectric.annotation.Config;
 
-import org.chromium.base.Callback;
 import org.chromium.base.MathUtils;
 import org.chromium.base.test.BaseRobolectricTestRunner;
 import org.chromium.chrome.browser.ActivityTabProvider;
-import org.chromium.chrome.browser.tab.Tab;
+import org.chromium.chrome.browser.ActivityTabProvider.ActivityTabObserver;
 import org.chromium.chrome.browser.tab.TabImpl;
 import org.chromium.chrome.browser.tab.TabObserver;
 import org.chromium.chrome.browser.toolbar.load_progress.LoadProgressProperties.CompletionState;
@@ -51,7 +50,7 @@ public class LoadProgressMediatorTest {
     @Captor
     public ArgumentCaptor<TabObserver> mTabObserverCaptor;
     @Captor
-    public ArgumentCaptor<Callback<Tab>> mActivityTabObserverCaptor;
+    public ArgumentCaptor<ActivityTabObserver> mActivityTabObserverCaptor;
 
     private PropertyModel mModel;
     private LoadProgressMediator mMediator;
@@ -94,7 +93,7 @@ public class LoadProgressMediatorTest {
     public void switchToLoadingTab() {
         doReturn(true).when(mTab2).isLoading();
         doReturn(0.1f).when(mTab2).getProgress();
-        mActivityTabObserverCaptor.getValue().onResult(mTab2);
+        mActivityTabObserverCaptor.getValue().onActivityTabChanged(mTab2, false);
         verify(mTab2, times(1)).addObserver(any());
 
         assertEquals(
@@ -111,7 +110,7 @@ public class LoadProgressMediatorTest {
         assertEquals(mModel.get(LoadProgressProperties.PROGRESS),
                 LoadProgressMediator.MINIMUM_LOAD_PROGRESS, MathUtils.EPSILON);
 
-        mActivityTabObserverCaptor.getValue().onResult(mTab2);
+        mActivityTabObserverCaptor.getValue().onActivityTabChanged(mTab2, false);
         verify(mTab2, times(1)).addObserver(any());
         assertEquals(mModel.get(LoadProgressProperties.COMPLETION_STATE),
                 CompletionState.FINISHED_DONT_ANIMATE);
@@ -142,7 +141,7 @@ public class LoadProgressMediatorTest {
                 LoadProgressMediator.MINIMUM_LOAD_PROGRESS, MathUtils.EPSILON);
 
         when(mTab2.getUrlString()).thenReturn(NATIVE_PAGE_URL);
-        mActivityTabObserverCaptor.getValue().onResult(mTab2);
+        mActivityTabObserverCaptor.getValue().onActivityTabChanged(mTab2, false);
         verify(mTab2, times(1)).addObserver(any());
         assertEquals(mModel.get(LoadProgressProperties.COMPLETION_STATE),
                 CompletionState.FINISHED_DONT_ANIMATE);