Remove duplication between Mandoline and mojo_runner main functions.

mojo/runner/BUILD.gn

 # Copyright 2014 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.
 
 import("//mojo/generate_mojo_shell_assets_list.gni")
 import("//mojo/public/mojo_application.gni")
 import("//testing/test.gni")
 import("//third_party/mojo/src/mojo/public/tools/bindings/mojom.gni")
 
 group("runner") {
@@ skipping 26 matching lines @@
     "//build/config/sanitizers:deps",
     "//mojo/common",
     "//mojo/environment:chromium",
     "//mojo/message_pump",
     "//mojo/runner/host:lib",
     "//mojo/runner/host:switches",
   ]
 
   if (!is_android) {
     sources += [
-      "desktop/launcher_process.cc",
-      "desktop/launcher_process.h",
       "desktop/main.cc",
       "register_local_aliases.cc",
       "register_local_aliases.h",
     ]
     deps += [
       "//components/tracing:startup_tracing",
       "//mojo/shell",
     ]
   } else {
     sources += [
@@ skipping 108 matching lines @@
       "android/ui_application_loader_android.cc",
       "android/ui_application_loader_android.h",
     ]
 
     deps += [
       ":jni_headers",
       ":run_android_application_function",
       "//components/mus/gles2",
       "//mojo/application/public/cpp:content_handler",
     ]
+  } else {
+    sources += [
+      "desktop/launcher_process.cc",
+      "desktop/launcher_process.h",
+      "desktop/main_helper.cc",
+      "desktop/main_helper.h",
+    ]
   }
 
   # This target includes some files behind #ifdef OS... guards. Since gn is not
   # smart enough to understand preprocess includes, it does complains about
   # these includes when not using the build files for that OS. Suppress checking
   # so we can enable checking for the rest of the targets in this file.
   # TODO: Might be better to split the files with OS-specific includes out to a
   # separate source_set so we can leave checking on for the rest of the target.
   check_includes = false
 }
@@ skipping 169 matching lines @@
   }
 
   generate_mojo_shell_assets_list("build_mojo_runner_test_assets") {
     testonly = true
     deps = [
       ":copy_mojo_runner_test_assets",
     ]
     dir = mojo_runner_test_assets_dir
   }
 }