Turn on verbose flag for compiling file_manager.

ui/file_manager/video_player/js/compiled_resources.gyp

Index: ui/file_manager/video_player/js/compiled_resources.gyp
diff --git a/ui/file_manager/video_player/js/compiled_resources.gyp b/ui/file_manager/video_player/js/compiled_resources.gyp
index 331001bf9780c9a9a50f0b92122e072e87c67706..99bb47242c6ad1efb14af8617ad595d6c8fe5fa5 100644
--- a/ui/file_manager/video_player/js/compiled_resources.gyp
+++ b/ui/file_manager/video_player/js/compiled_resources.gyp
@@ -40,6 +40,9 @@
           '../../externs/es6_workaround.js',
           '../../externs/platform.js',
         ],
+        'closure_args': [
+          'warning_level=VERBOSE'
+        ]
       },
       'includes': [
         '../../../../third_party/closure_compiler/compile_js.gypi'
@@ -101,6 +104,9 @@
           '../../externs/platform.js',
           '../../externs/video_player_foreground.js',
         ],
+        'closure_args': [
+          'warning_level=VERBOSE'
+        ]
       },
       'includes': [
         '../../../../third_party/closure_compiler/compile_js.gypi'