Show Floating action button to request manage credentials

Background
* This is part of the work to support
  a credential management app on
  unmanaged devices.
Changes
* Show FAB for detailed/long manage credentials
  authentication policy.
* Hide FAB for short manage credentials
  authentication policy.
* Unexpand FAB once the user start starts
  scrolling.
* Hide FAB once the user has scrolled to
  the bottom.

Manual Testing
* Verify FAB is shown for a detailed/long policy:
  https://screenshot.googleplex.com/BUb4LGz3GD6AozS
* Verify FAB is hidden for a short policy
* Verify FAB is hidden when user has scrolled to the
  bottom:
  https://screenshot.googleplex.com/6FQRqto3r3jzfXH
* Verify FAB is unexpanded (text hidden)
  when the users start scrolling:
  https://screenshot.googleplex.com/4FfAt5MsCfrAwQK

Bug: 165641221
Test: Manual Testing
      make RunSettingsRoboTests -j ROBOTEST_FILTER=com.android.settings.security.RequestManageCredentialsTest
Change-Id: Ied2ef726ad4dcc3f92c20249f80294f0a3071a8a

src/com/android/settings/security/RequestManageCredentials.java

@@ -35,6 +35,8 @@ import androidx.recyclerview.widget.RecyclerView;
 
 import com.android.settings.R;
 
+import com.google.android.material.floatingactionbutton.ExtendedFloatingActionButton;
+
 /**
  * Displays a full screen to the user asking whether the calling app can manage the user's
  * KeyChain credentials. This screen includes the authentication policy highlighting what apps and
@@ -62,6 +64,7 @@ public class RequestManageCredentials extends Activity {
     private RecyclerView mRecyclerView;
     private LinearLayoutManager mLayoutManager;
     private LinearLayout mButtonPanel;
+    private ExtendedFloatingActionButton mExtendedFab;
 
     private boolean mDisplayingButtonPanel = false;
 
@@ -79,6 +82,7 @@ public class RequestManageCredentials extends Activity {
 
             loadRecyclerView();
             loadButtons();
+            loadExtendedFloatingActionButton();
             addOnScrollListener();
         } else {
             Log.e(TAG, "Unable to start activity because intent action is not "
@@ -106,6 +110,15 @@ public class RequestManageCredentials extends Activity {
         allowButton.setOnClickListener(setCredentialManagementApp());
     }
 
+    private void loadExtendedFloatingActionButton() {
+        mExtendedFab = findViewById(R.id.extended_fab);
+        mExtendedFab.setOnClickListener(v -> {
+            mRecyclerView.scrollToPosition(mAuthenticationPolicy.getAppAndUriMappings().size());
+            mExtendedFab.hide();
+            showButtonPanel();
+        });
+    }
+
     private View.OnClickListener finishRequestManageCredentials() {
         return v -> {
             Toast.makeText(this, R.string.request_manage_credentials_dont_allow,
@@ -130,9 +143,16 @@ public class RequestManageCredentials extends Activity {
             public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
                 super.onScrolled(recyclerView, dx, dy);
                 if (!mDisplayingButtonPanel) {
+                    // On down scroll, hide text in floating action button by setting
+                    // extended to false.
+                    if (dy > 0 && mExtendedFab.getVisibility() == View.VISIBLE) {
+                        mExtendedFab.setExtended(false);
+                    }
                     if (isRecyclerScrollable()) {
+                        mExtendedFab.show();
                         hideButtonPanel();
                     } else {
+                        mExtendedFab.hide();
                         showButtonPanel();
                     }
                 }