Adds 4 additional MDC icons needed by FeedbackKit V2

Bug: 657076
Change-Id: Iebbc85ea1061ef2a00479d80eecd038d78a6c548
Reviewed-on: https://chromium-review.googlesource.com/926042Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Peter Lee <pkl@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537771}

third_party/material_design_icons/BUILD.gn

@@ -14,6 +14,7 @@ _image_sets = [
   "action/ic_account_circle",
   "action/ic_account_circle_48pt",
   "action/ic_delete",
+  "action/ic_done",
   "action/ic_feedback",
   "action/ic_help",
   "action/ic_info",
@@ -28,10 +29,13 @@ _image_sets = [
   "communication/ic_email",
   "communication/ic_message",
   "content/ic_link",
+  "content/ic_send",
+  "content/ic_undo",
   "editor/ic_mode_edit",
   "file/ic_file_download",
   "hardware/ic_desktop_windows",
   "hardware/ic_desktop_windows_white",
+  "hardware/ic_keyboard_arrow_down",
   "hardware/ic_keyboard_arrow_right",
   "hardware/ic_mouse",
   "image/ic_photo_camera",