remove libwebm third_party dependency

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 278 matching lines @@
 
   'src/third_party/mesa/src':
    Var('chromium_git') + '/chromium/deps/mesa.git' + '@' + '9731cb962963bca8a05f3d0f6ea40c3a781f0537',
 
   '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',
 
-  'src/third_party/libwebm/source':
-   Var('chromium_git') + '/webm/libwebm.git' + '@' + '0d4cb404ea4195e5e21d04db2c955615535ce62e',
-
   'src/third_party/pdfium':
    'https://pdfium.googlesource.com/pdfium.git' + '@' +  Var('pdfium_revision'),
 
   'src/third_party/boringssl/src':
    'https://boringssl.googlesource.com/boringssl.git' + '@' +  Var('boringssl_revision'),
 
   'src/third_party/py_trace_event/src':
     Var('chromium_git') + '/external/py_trace_event.git' + '@' + 'dd463ea9e2c430de2b9e53dea57a77b4c3ac9b30',
 }
 
@@ skipping 473 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',
     ],
   },
 ]