Add ffmpegsumo.dll to 'symsrc' group for symbol upload.

chrome/tools/build/win/FILES.cfg

 # -*- python -*-
 # ex: set syntax=python:
 
 # Copyright (c) 2012 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.
 
 # This is a buildbot configuration file containing a tagged list of files
 # processed by the stage/archive scripts. The known tags are:
 #
@@ skipping 22 matching lines @@
   {
     'filename': 'app_host.exe',
     'arch': ['32bit', '64bit'],
     'buildtype': ['dev', 'official'],
     'filegroup': ['default', 'symsrc'],
   },
   {
     'filename': 'ffmpegsumo.dll',
     'arch': ['32bit', '64bit'],
     'buildtype': ['dev', 'official'],
+    'filegroup': ['default', 'symsrc'],
   },
   {
     'filename': 'chrome.exe',
     'arch': ['32bit', '64bit'],
     'buildtype': ['dev', 'official'],
     'filegroup': ['default', 'symsrc'],
   },
   {
     'filename': 'nacl64.exe',
     'arch': ['32bit', '64bit'],
@@ skipping 719 matching lines @@
     'buildtype': ['official'],
     'archive': 'chrome-win32-syms.zip',
   },
   {
     'filename': 'syzygy/mini_installer.exe.pdb',
     'arch': ['32bit', '64bit'],
     'buildtype': ['official'],
     'archive': 'chrome-win32-syms.zip',
   },
 ]