Convert mus apptests to shelltests

components/mus/public/cpp/tests/BUILD.gn

Index: components/mus/public/cpp/tests/BUILD.gn
diff --git a/components/mus/public/cpp/tests/BUILD.gn b/components/mus/public/cpp/tests/BUILD.gn
index f89b23fb71f4e9fd255270befa324c5bb9f061f7..d0c6a057ec133b0b889d9e034abcfc8b8d750e13 100644
--- a/components/mus/public/cpp/tests/BUILD.gn
+++ b/components/mus/public/cpp/tests/BUILD.gn
@@ -20,6 +20,8 @@ source_set("test_support") {
   testonly = true
 
   sources = [
+    "window_server_shelltest_base.cc",
+    "window_server_shelltest_base.h",
     "window_server_test_base.cc",
     "window_server_test_base.h",
   ]
@@ -27,10 +29,13 @@ source_set("test_support") {
   deps = [
     "//base",
     "//base/test:test_config",
+    "//components/mus/common:mus_common",
     "//components/mus/public/cpp",
+    "//mojo/shell/public/cpp:shell_test_support",
     "//mojo/shell/public/cpp:sources",
     "//mojo/shell/public/cpp:test_support",
     "//testing/gtest",
+    "//ui/gl",
   ]
 }