Moves NativeViewportApplicationLoader into own files

shell/BUILD.gn

Index: shell/BUILD.gn
diff --git a/shell/BUILD.gn b/shell/BUILD.gn
index c9856e0873cbce95353bcd1b8700899222260235..4506cc22e2e009cb489b30b6c59a1535ebf154ca 100644
--- a/shell/BUILD.gn
+++ b/shell/BUILD.gn
@@ -68,6 +68,8 @@ if (!use_prebuilt_mojo_shell) {
 
       deps += [
         ":jni_headers",
+        "//mojo/application_manager:application_manager",
+        "//services/native_viewport:lib",
         "//ui/gl",
       ]
     }
@@ -194,6 +196,8 @@ source_set("lib") {
       "android/android_handler.h",
       "android/android_handler_loader.cc",
       "android/android_handler_loader.h",
+      "android/native_viewport_application_loader.cc",
+      "android/native_viewport_application_loader.h",
       "android/ui_application_loader_android.cc",
       "android/ui_application_loader_android.h",
     ]
@@ -254,6 +258,10 @@ if (is_android) {
     sources = [
       "android/run_android_application_function.h",
     ]
+
+    deps = [
+      "//base",
+    ]
   }
 
   android_library("java") {