Closes “Close All” confirmation dialog after 3D Force touch

This CL closes the "Close All" confirmationActionSheet when the app is
running on background.

Bug: 1133304
Change-Id: I20ca7342ea74c14615379f97acdcf8ba02a67fec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2442532
Commit-Queue: Ewann Pellé <ewannpv@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#813240}

ios/chrome/browser/ui/tab_grid/tab_grid_coordinator.mm

@@ -436,6 +436,13 @@
                          message:nil
                             rect:self.baseViewController.view.frame
                             view:self.baseViewController.view];
+
+  NSNotificationCenter* defaultCenter = [NSNotificationCenter defaultCenter];
+  [defaultCenter addObserver:self
+                    selector:@selector(applicationDidEnterBackground:)
+                        name:UIApplicationDidEnterBackgroundNotification
+                      object:nil];
+
   self.actionSheetCoordinator.popoverArrowDirection = 0;
   self.actionSheetCoordinator.alertStyle =
       IsIPadIdiom() ? UIAlertControllerStyleAlert
@@ -488,6 +495,12 @@
                  focusOmnibox:NO];
 }
 
+#pragma mark - Notification callback
+
+- (void)applicationDidEnterBackground:(NSNotification*)notification {
+  [self.actionSheetCoordinator stop];
+}
+
 #pragma mark - HistoryPresentationDelegate
 
 - (void)showActiveRegularTabFromHistory {