[MDC iOS] Add MDCCardCollectionCell

This is needed by internal classes.

Bug: 950898
Change-Id: I50f784c8656b3e330f412c741acfc3625cc8590b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1559957
Auto-Submit: Olivier Robin <olivierrobin@chromium.org>
Commit-Queue: Peter Lee <pkl@chromium.org>
Reviewed-by: Peter Lee <pkl@chromium.org>
Cr-Commit-Position: refs/heads/master@{#649190}

ios/third_party/material_components_ios/BUILD.gn

@@ -184,6 +184,8 @@ source_set("material_components_ios") {
     "src/components/Cards/src/ColorThemer/MDCCardsColorThemer.m",
     "src/components/Cards/src/MDCCard.h",
     "src/components/Cards/src/MDCCard.m",
+    "src/components/Cards/src/MDCCardCollectionCell.h",
+    "src/components/Cards/src/MDCCardCollectionCell.m",
     "src/components/CollectionCells/src/MDCCollectionViewCell.h",
     "src/components/CollectionCells/src/MDCCollectionViewCell.m",
     "src/components/CollectionCells/src/MDCCollectionViewTextCell.h",