Use MDC CollectionCells bundle.

ios/third_party/material_components_ios/BUILD.gn

Index: ios/third_party/material_components_ios/BUILD.gn
diff --git a/ios/third_party/material_components_ios/BUILD.gn b/ios/third_party/material_components_ios/BUILD.gn
index 900488c81acd37d6d0ee8bb8b4ff1f9b5ae9bd48..7d25a604c082d0458435852d0bc1b08c32964234 100644
--- a/ios/third_party/material_components_ios/BUILD.gn
+++ b/ios/third_party/material_components_ios/BUILD.gn
@@ -248,6 +248,7 @@ source_set("material_components_ios") {
   ]
 
   deps = [
+    ":material_collection_cells_bundle",
     ":material_collections_bundle",
     ":material_component_ic_arrow_back_bundle",
     "//ios/third_party/material_text_accessibility_ios",
@@ -267,14 +268,46 @@ source_set("material_components_ios") {
   ]
 }
 
-bundle_data("material_collections_bundle") {
+_locales = [ "en" ]
+
+foreach(locale, _locales) {

[lpromero, 2017/03/23 12:12:36]

Is it OK to use the same for loop for both bundle_data targets? Or do you prefer
one foreach for each?

[sdefresne, 2017/03/23 15:55:44]

It's fine using the same loop (we can always split it if the list of supported
locales is different).

+  bundle_data("material_collections_bundle_$locale") {
+    visibility = [ ":material_collections_bundle" ]
+    sources = [
+      "src/components/Collections/src/MaterialCollections.bundle/Resources/$locale.lproj/MaterialCollections.strings",
+    ]
+    outputs = [
+      "{{bundle_root_dir}}/MaterialCollections.bundle/Resources/$locale.lproj/{{source_file_part}}",
+    ]
+  }
+
+  bundle_data("material_collection_cells_bundle_$locale") {
+    visibility = [ ":material_collection_cells_bundle" ]
+    sources = [
+      "src/components/CollectionCells/src/MaterialCollectionCells.bundle/Resources/$locale.lproj/MaterialCollectionCells.strings",
+    ]
+    outputs = [
+      "{{bundle_resources_dir}}/MaterialCollectionCells.bundle/Resources/$locale.lproj/{{source_file_part}}",
+    ]
+  }
+}
+
+group("material_collections_bundle") {
   visibility = [ ":material_components_ios" ]
-  sources = [
-    "src/components/Collections/src/MaterialCollections.bundle/Resources/en.lproj/MaterialCollections.strings",
-  ]
-  outputs = [
-    "{{bundle_root_dir}}/MaterialCollections.bundle/Resources/en.lproj/{{source_file_part}}",
-  ]
+
+  deps = []
+  foreach(locale, _locales) {
+    deps += [ ":material_collections_bundle_$locale" ]
+  }
+}
+
+group("material_collection_cells_bundle") {
+  visibility = [ ":material_components_ios" ]
+
+  deps = []
+  foreach(locale, _locales) {
+    deps += [ ":material_collection_cells_bundle_$locale" ]
+  }
 }
 
 # TODO(crbug.com/662421): Move back to _icon_names when there is just one