[ios] Grid cell needs to reset before reuse

Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I808e52f47db5dbc9ddc609b123be1e10dabde996
Reviewed-on: https://chromium-review.googlesource.com/967889Reviewed-by: edchin <edchin@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Commit-Queue: edchin <edchin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#544083}

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

@@ -82,6 +82,15 @@
   // NO-OP to disable highlighting and only allow selection.
 }
 
+- (void)prepareForReuse {
+  [super prepareForReuse];
+  self.itemIdentifier = nil;
+  self.title = nil;
+  self.icon = nil;
+  self.snapshot = nil;
+  self.selected = NO;
+}
+
 #pragma mark - Accessibility
 
 - (BOOL)isAccessibilityElement {