Add a dependency for FlatBuffers.

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 191 matching lines @@
 
   'src/third_party/yasm/source/patched-yasm':
    Var('chromium_git') + '/chromium/deps/yasm/patched-yasm.git' + '@' + '7da28c6c7c6a1387217352ce02b31754deb54d2a',
 
   'src/third_party/libjpeg_turbo':
    Var('chromium_git') + '/chromium/deps/libjpeg_turbo.git' + '@' + 'e4e75037f29745f1546b6ebf5cf532e841c04c2c',
 
   'src/third_party/flac':
    Var('chromium_git') + '/chromium/deps/flac.git' + '@' + '2c4b86af352b23498315c016dc207e3fb2733fc0',
 
+  'src/third_party/flatbuffers/src':
+   Var('chromium_git') + '/external/github.com/google/flatbuffers.git' + '@' + '6f751d5d26fd566f8c9060358101a2596677f9cf',
+
   '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' + '@' + '590e847a1bcf77039ac2760e0e308bd12b46cf09', # commit position 12359
 
   'src/third_party/openmax_dl':
@@ skipping 616 matching lines @@
     'pattern': '\\.sha1',
     'action': ['python', 'src/third_party/instrumented_libraries/scripts/download_binaries.py'],
   },
   {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
     'name': 'gyp',
     'pattern': '.',
     'action': ['python', 'src/build/gyp_chromium', '--running-as-hook'],
   },
 ]