[Signin][Android] Destroy account picker bottomsheet in observer

This CL destroys the account picker bottomsheet by registering a
BottomSheetObserver object in BottomSheetController.

Bug: 1063362
Change-Id: Ibfcc6e27fc8c5438589d49f4e753b76321d5604c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2241653
Commit-Queue: Alice Wang <aliceywang@chromium.org>
Reviewed-by: Boris Sazonov <bsazonov@chromium.org>
Reviewed-by: Matthew Jones <mdjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#779304}

chrome/android/java/src/org/chromium/chrome/browser/signin/account_picker/AccountPickerBottomSheetCoordinator.java

@@ -9,6 +9,8 @@ import android.content.Context;
 import androidx.annotation.MainThread;
 
 import org.chromium.chrome.browser.widget.bottomsheet.BottomSheetController;
+import org.chromium.chrome.browser.widget.bottomsheet.BottomSheetObserver;
+import org.chromium.chrome.browser.widget.bottomsheet.EmptyBottomSheetObserver;
 import org.chromium.ui.modelutil.PropertyModel;
 import org.chromium.ui.modelutil.PropertyModelChangeProcessor;
 
@@ -17,6 +19,16 @@ import org.chromium.ui.modelutil.PropertyModelChangeProcessor;
  */
 public class AccountPickerBottomSheetCoordinator {
     private final AccountPickerCoordinator mAccountPickerCoordinator;
+    private final BottomSheetController mBottomSheetController;
+    private final BottomSheetObserver mBottomSheetObserver = new EmptyBottomSheetObserver() {
+        @Override
+        public void onSheetStateChanged(int newState) {
+            super.onSheetStateChanged(newState);
+            if (newState == BottomSheetController.SheetState.HIDDEN) {
+                AccountPickerBottomSheetCoordinator.this.destroy();
+            }
+        }
+    };
 
     /**
      * Constructs the AccountPickerBottomSheetCoordinator and shows the
@@ -29,16 +41,19 @@ public class AccountPickerBottomSheetCoordinator {
         AccountPickerBottomSheetView view = new AccountPickerBottomSheetView(context);
         mAccountPickerCoordinator = new AccountPickerCoordinator(
                 view.getAccountPickerItemView(), accountPickerListener, null);
+        mBottomSheetController = bottomSheetController;
         PropertyModel model = AccountPickerBottomSheetProperties.createModel();
         PropertyModelChangeProcessor.create(model, view, AccountPickerBottomSheetViewBinder::bind);
-        bottomSheetController.requestShowContent(view, true);
+        mBottomSheetController.addObserver(mBottomSheetObserver);
+        mBottomSheetController.requestShowContent(view, true);
     }
 
     /**
      * Releases the resources used by AccountPickerBottomSheetCoordinator.
      */
     @MainThread
-    public void destroy() {
+    private void destroy() {
         mAccountPickerCoordinator.destroy();
+        mBottomSheetController.removeObserver(mBottomSheetObserver);
     }
 }

chrome/android/javatests/src/org/chromium/chrome/browser/signin/AccountPickerBottomSheetTest.java

@@ -15,7 +15,6 @@ import static org.mockito.MockitoAnnotations.initMocks;
 
 import androidx.test.filters.MediumTest;
 
-import org.junit.After;
 import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
@@ -86,13 +85,6 @@ public class AccountPickerBottomSheetTest {
                         mAccountPickerListenerMock);
     }
 
-    @After
-    public void tearDown() {
-        if (mAccountPickerBottomSheetCoordinator != null) {
-            TestThreadUtils.runOnUiThreadBlocking(mAccountPickerBottomSheetCoordinator::destroy);
-        }
-    }
-
     @Test
     @MediumTest
     public void testTitle() {