Simplify mojo_shell since it's now only used for Mandoline.

mojo/services/window_manager/BUILD.gn

Index: mojo/services/window_manager/BUILD.gn
diff --git a/mojo/services/window_manager/BUILD.gn b/mojo/services/window_manager/BUILD.gn
index c34ebe1513ca90f44dcc8ca4bb27c003df4f4d98..bb6df15b5aa5dd2c2f26a4885ad447b73cd98614 100644
--- a/mojo/services/window_manager/BUILD.gn
+++ b/mojo/services/window_manager/BUILD.gn
@@ -6,23 +6,6 @@ import("//build/config/ui.gni")
 import("//third_party/mojo/src/mojo/public/mojo_application.gni")
 import("//testing/test.gni")
 
-mojo_native_application("window_manager") {
-  sources = [
-    "main.cc",
-  ]
-
-  public_deps = [
-    ":lib",
-  ]
-
-  deps = [
-    "//base",
-    "//mojo/application",
-    "//mojo/common:tracing_impl",
-    "//third_party/mojo_services/src/view_manager/public/cpp",
-  ]
-}
-
 source_set("lib") {
   sources = [
     "basic_focus_rules.cc",
@@ -108,6 +91,24 @@ test("window_manager_unittests") {
   }
 }
 
+# A basic window manager with a default delegate used for testing.
+mojo_native_application("test_window_manager") {
+  sources = [
+    "main.cc",
+  ]
+
+  public_deps = [
+    ":lib",
+  ]
+
+  deps = [
+    "//base",
+    "//mojo/application",
+    "//mojo/common:tracing_impl",
+    "//third_party/mojo_services/src/view_manager/public/cpp",
+  ]
+}
+
 mojo_native_application("window_manager_apptests") {
   testonly = true
 
@@ -125,5 +126,5 @@ mojo_native_application("window_manager_apptests") {
     "//third_party/mojo_services/src/window_manager/public/interfaces",
   ]
 
-  data_deps = [ ":window_manager($default_toolchain)" ]
+  data_deps = [ ":test_window_manager($default_toolchain)" ]
 }