Add 2x icons resources to mash.

ash/mus/BUILD.gn

Index: ash/mus/BUILD.gn
diff --git a/ash/mus/BUILD.gn b/ash/mus/BUILD.gn
index e7ad2dc86a77a16e6d623963e95057b75dddf5a6..38dc043461c4bb410a1df3c59875aa8cf4bcc6d5 100644
--- a/ash/mus/BUILD.gn
+++ b/ash/mus/BUILD.gn
@@ -149,6 +149,7 @@ service("mus") {
   deps = [
     ":lib",
     ":resources",
+    ":resources_200",
     "//services/shell/public/cpp",
   ]
 
@@ -159,7 +160,10 @@ service("mus") {
     "//services/ui",
   ]
 
-  resources = [ "$root_out_dir/ash_mus_resources.pak" ]
+  resources = [
+    "$root_out_dir/ash_mus_resources.pak",
+    "$root_out_dir/ash_mus_resources_200.pak",
+  ]
 }
 
 service_manifest("manifest") {
@@ -167,7 +171,7 @@ service_manifest("manifest") {
   source = "manifest.json"
 }
 
-# TODO: Load resources at additional scales and load locale-specific strings.
+# TODO: Load locale-specific strings.
 # TODO: Avoid duplication between Mash and Chrome pak files: crbug.com/628715.
 repack("resources") {
   output = "$root_out_dir/ash_mus_resources.pak"
@@ -189,6 +193,20 @@ repack("resources") {
   ]
 }
 
+repack("resources_200") {
+  output = "$root_out_dir/ash_mus_resources_200.pak"
+  sources = [
+    "$root_gen_dir/ash/resources/ash_resources_200_percent.pak",
+    "$root_gen_dir/ui/resources/ui_resources_200_percent.pak",
+    "$root_gen_dir/ui/views/resources/views_resources_200_percent.pak",
+  ]
+  deps = [
+    "//ash/resources",
+    "//ui/resources",
+    "//ui/views/resources",
+  ]
+}
+
 source_set("unittests") {
   testonly = true