Close snackbar when the user initiates the closing of a Tab

Currently we don't do this and it means the user can group tabs,
close one of the tabs in the group and then undo the grouping.
Because one of the tabs is destroyed this leads to a crash when
we try to update its root id.

Bug: 1117396
Change-Id: I0d91d44ce2bf8783531ccb3c959010fdf6905fb3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2414995
Commit-Queue: David Maunder <davidjm@chromium.org>
Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#808090}

chrome/android/features/tab_ui/java/src/org/chromium/chrome/browser/tasks/tab_management/UndoGroupSnackbarController.java

@@ -98,6 +98,12 @@ public class UndoGroupSnackbarController implements SnackbarManager.SnackbarCont
                                 UndoGroupSnackbarController.this);
                     }
 
+                    @Override
+                    public void willCloseTab(Tab tab, boolean animate) {
+                        mSnackbarManageable.getSnackbarManager().dismissSnackbars(
+                                UndoGroupSnackbarController.this);
+                    }
+
                     @Override
                     public void didCloseTab(int tabId, boolean incognito) {
                         mSnackbarManageable.getSnackbarManager().dismissSnackbars(