Roll ffmpeg DEPS for security fix.

DEPS

 # This file is used to manage the dependencies of the Chromium src repo. It is
 # used by gclient to determine what version of each dependency to check out, and
 # where.
 #
 # For more information, please refer to the official documentation:
 #   https://sites.google.com/a/chromium.org/dev/developers/how-tos/get-the-code
 #
 # When adding a new dependency, please update the top-level .gitignore file
 # to list the dependency's destination directory.
 #
@@ skipping 179 matching lines @@
   'src/third_party/webdriver/pylib':
     Var('chromium_git') + '/external/selenium/py.git' + '@' + '5fd78261a75fe08d27ca4835fb6c5ce4b42275bd',
 
   'src/third_party/libvpx':
    Var('chromium_git') + '/chromium/deps/libvpx.git' + '@' +  Var('libvpx_revision'),
 
   'src/third_party/libvpx_new/source/libvpx':
    Var('chromium_git') + '/webm/libvpx.git' + '@' +  '7d28d12ef34f6cbb6b1e18f3b23b71392fd3ddf5',
 
   'src/third_party/ffmpeg':
-   Var('chromium_git') + '/chromium/third_party/ffmpeg.git' + '@' + 'cf1d457c7dfbcc65c26fad16baef881c7b0bab3a',
+   Var('chromium_git') + '/chromium/third_party/ffmpeg.git' + '@' + '525a71ab8ee3b61da48138f7e1c406989d2879fc',
 
   'src/third_party/libjingle/source/talk':
     Var('chromium_git') + '/external/webrtc/trunk/talk.git' + '@' + 'c1f29d891d2d439060eff868e34935f69d454cca', # commit position 10116
 
   'src/third_party/usrsctp/usrsctplib':
     Var('chromium_git') + '/external/usrsctplib.git' + '@' + '36444a999739e9e408f8f587cb4c3ffeef2e50ac', # from svn revision 9215
 
   'src/third_party/libsrtp':
    Var('chromium_git') + '/chromium/deps/libsrtp.git' + '@' + '502e81a238a864cfce774d4de3893810629bf227', # from svn revision 295151
 
@@ skipping 603 matching lines @@
     'pattern': '.',
     'action': [
         'python',
         'src/tools/check_git_config.py',
         '--running-as-hook',
     ],
   },
 ]