[ios] Take snapshot for tab grid.

ios/clean/chrome/browser/ui/tab_collection/BUILD.gn

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 source_set("tab_collection") {
   sources = [
     "tab_collection_mediator.h",
     "tab_collection_mediator.mm",
   ]
   deps = [
     ":tab_collection_ui",
     "//base",
+    "//ios/chrome/browser/snapshots",
     "//ios/chrome/browser/web",
     "//ios/chrome/browser/web_state_list",
     "//ios/web",
+    "//ui/gfx",
   ]
   configs += [ "//build/config/compiler:enable_arc" ]
 }
 
 source_set("tab_collection_ui") {
   sources = [
     "tab_collection_consumer.h",
     "tab_collection_item.h",
     "tab_collection_item.mm",
     "tab_collection_tab_cell.h",
@@ skipping 33 matching lines @@
     "//ios/chrome/test/base",
     "//ios/web/public/test/fakes",
     "//testing/gtest",
     "//third_party/ocmock",
     "//ui/base:test_support",
     "//url:url",
   ]
   configs += [ "//build/config/compiler:enable_arc" ]
   testonly = true
 }