[Android][Mfill] Fix a bug in AllPasswordsBottomSheetViewTest

This CL fixes this bug crbug.com/1127200. Which arise when
`View.setOnClickListener(null)` is called. This causes the view
to become clickable again, even though no click listener exists.

TBR=fhorschig@chromium.org

Bug: 1127200
Change-Id: I0eb0a404346aa97830c29ac0cf4f959c40e06beb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2405581Reviewed-by: Ioana Pandele <ioanap@chromium.org>
Commit-Queue: Reda Tawfik <redatawfik@google.com>
Commit-Queue: Ioana Pandele <ioanap@chromium.org>
Cr-Commit-Position: refs/heads/master@{#806223}

chrome/android/features/keyboard_accessory/internal/java/src/org/chromium/chrome/browser/keyboard_accessory/all_passwords_bottom_sheet/AllPasswordsBottomSheetViewBinder.java

@@ -104,10 +104,15 @@ class AllPasswordsBottomSheetViewBinder {
                 passwordView.setOnClickListener(
                         src -> model.get(ON_CLICK_LISTENER).onResult(credential));
                 usernameView.setOnClickListener(null);
+                usernameView.setClickable(false);
             } else {
-                usernameView.setOnClickListener(
-                        src -> model.get(ON_CLICK_LISTENER).onResult(credential));
+                String username = credential.getUsername();
+                usernameView.setOnClickListener(username.isEmpty()
+                                ? null
+                                : src -> model.get(ON_CLICK_LISTENER).onResult(credential));
+                usernameView.setClickable(!username.isEmpty());
                 passwordView.setOnClickListener(null);
+                passwordView.setClickable(false);
             }
         } else if (propertyKey == IS_PASSWORD_FIELD) {
             boolean isPasswordField = model.get(IS_PASSWORD_FIELD);