[Collections] Updates layout logic to include isEditing, thereby forc…

…ing infoBar positions to get updated.

Reviewers: #mdc_ios_owners, ajsecord

Reviewed By: #mdc_ios_owners, ajsecord

Projects: #material_components_ios

Differential Revision: http://codereview.cc/D819

components/Collections/src/MDCCollectionViewFlowLayout.m

@@ -111,7 +111,8 @@ - (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect {
 }
 
 - (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds {
-  if (!CGSizeEqualToSize(self.collectionView.bounds.size, newBounds.size)) {
+  if (!CGSizeEqualToSize(self.collectionView.bounds.size, newBounds.size) ||
+      self.editor.isEditing) {
     return YES;
   }
   return NO;