Update Chromium for webrtc r7656.

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 226 matching lines @@
   'src/third_party/flac':
    Var('chromium_git') + '/chromium/deps/flac.git' + '@' + '0635a091379d9677f1ddde5f2eec85d0f096f219',
 
   'src/third_party/pyftpdlib/src':
     Var('chromium_git') + '/external/pyftpdlib.git' + '@' + '2be6d65e31c7ee6320d059f581f05ae8d89d7e45',
 
   'src/third_party/scons-2.0.1':
    Var('chromium_git') + '/native_client/src/third_party/scons-2.0.1.git' + '@' + '1c1550e17fc26355d08627fbdec13d8291227067',
 
   'src/third_party/webrtc':
-    Var('chromium_git') + '/external/webrtc/trunk/webrtc.git' + '@' + 'b831a9e3d5f9f0563d249b726cffa8a070e58aee', # from svn revision 7638
+    Var('chromium_git') + '/external/webrtc/trunk/webrtc.git' + '@' + '8645a5afa00d4ccb32f7630a91d7bb039147b632', # from svn revision 7656
 
   'src/third_party/openmax_dl':
     Var('chromium_git') + '/external/webrtc/deps/third_party/openmax.git' + '@' +  Var('openmax_dl_revision'),
 
   'src/third_party/jsoncpp/source/include':
     Var('chromium_git') + '/external/jsoncpp/jsoncpp/include.git' + '@' + 'b0dd48e02b6e6248328db78a65b5c601f150c349',
 
   'src/third_party/jsoncpp/source/src/lib_json':
     Var('chromium_git') + '/external/jsoncpp/jsoncpp/src/lib_json.git' + '@' + 'a8caa51ba2f80971a45880425bf2ae864a786784',
 
@@ skipping 516 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',
     ],
   },
 ]