Implement OnLegacySessionError() in CdmAdapter.

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 267 matching lines @@
   'src/third_party/webpagereplay':
    Var('chromium_git') + '/external/web-page-replay.git' + '@' + '2f7b704b8b567983c040f555d3e46f9766db8e87',
 
   'src/third_party/pywebsocket/src':
     Var('chromium_git') + '/external/pywebsocket/src.git' + '@' + 'cb349e87ddb30ff8d1fa1a89be39cec901f4a29c',
 
   'src/third_party/opus/src':
    Var('chromium_git') + '/chromium/deps/opus.git' + '@' + 'cae696156f1e60006e39821e79a1811ae1933c69',
 
   'src/media/cdm/ppapi/api':
-   Var('chromium_git') + '/chromium/cdm.git' + '@' + '09203a77eb272cd112faa401428c6b5e8fb8b437', # from svn revision 293431
+   Var('chromium_git') + '/chromium/cdm.git' + '@' + '4aca5940e0a4f25c8ab3a91ffed3a59b0f7f6800', # from svn revision 293568
 
   'src/third_party/mesa/src':
    Var('chromium_git') + '/chromium/deps/mesa.git' + '@' + '071d25db04c23821a12a8b260ab9d96a097402f0',
 
   'src/third_party/cld_2/src':
     Var('chromium_git') + '/external/cld2.git' + '@' + '14d9ef8d4766326f8aa7de54402d1b9c782d4481', # from svn revision 193
 
   'src/chrome/browser/resources/pdf/html_office':
     Var('chromium_git') + '/chromium/html-office-public.git' + '@' + 'eeff97614f65e0578529490d44d412032c3d7359',
 
@@ skipping 495 matching lines @@
     # corresponding .py files have already been deleted.
     'name': 'remove_stale_pyc_files',
     'pattern': 'src/tools/.*\\.py',
     'action': [
         'python',
         'src/tools/remove_stale_pyc_files.py',
         'src/tools',
     ],
   },
 ]