Video Player: Use external entries instead of isolated entries

ui/file_manager/video_player/manifest.json

Index: ui/file_manager/video_player/manifest.json
diff --git a/ui/file_manager/video_player/manifest.json b/ui/file_manager/video_player/manifest.json
index 2d7e8b2c0d1247577b7246e67517d80d39fb0f69..66132c6d37d33bf84dbee595f8126fe885b505e7 100644
--- a/ui/file_manager/video_player/manifest.json
+++ b/ui/file_manager/video_player/manifest.json
@@ -48,9 +48,6 @@
   "app": {
     "background": {
       "scripts": [
-        "js/error_util.js",
-        "js/test_util.js",
-        "js/background.js",
         "chrome://resources/js/cr.js",
         "chrome://resources/js/cr/event_target.js",
         "chrome://resources/js/cr/ui/array_data_model.js",
@@ -59,7 +56,11 @@
         "chrome-extension://hhaomjibdihmijegdhdafkllkbggdgoj/common/js/async_util.js",
         "chrome-extension://hhaomjibdihmijegdhdafkllkbggdgoj/common/js/volume_manager_common.js",
         "chrome-extension://hhaomjibdihmijegdhdafkllkbggdgoj/background/js/volume_manager.js",
-        "chrome-extension://hhaomjibdihmijegdhdafkllkbggdgoj/foreground/js/file_type.js"
+        "chrome-extension://hhaomjibdihmijegdhdafkllkbggdgoj/foreground/js/file_type.js",
+        "js/error_util.js",
+        "js/test_util.js",
+        // The main background script must be at the end.
+        "js/background.js"
       ]
     },
     // The following ids are cast extension's ids .