Sync gflags into the right location.

DEPS

 vars = {
   # Override root_dir in your .gclient's custom_vars to specify a custom root
   # folder name.
   'root_dir': 'libyuv',
   'extra_gyp_flag': '-Dextra_gyp_flag=0',
   'chromium_git': 'https://chromium.googlesource.com',
 
   # Roll the Chromium Git hash to pick up newer versions of all the
   # dependencies and tools linked to in setup_links.py.
   'chromium_revision': 'bb79186c63ff4eff7a2a318a21731005c53f269b',
 }
 
 # NOTE: Prefer revision numbers to tags for svn deps. Use http rather than
 # https; the latter can cause problems for users behind proxies.
 deps = {
-  'src/third_party/gflags/src':
+  Var('root_dir') + '/third_party/gflags/src':
     Var('chromium_git') + '/external/gflags/src@e7390f9185c75f8d902c05ed7d20bb94eb914d0c', # from svn revision 82
 }
 
 # Define rules for which include paths are allowed in our source.
 include_rules = [ '+gflags' ]
 
 hooks = [
   {
     # Clone chromium and its deps.
     'name': 'sync chromium',
     'pattern': '.',
     'action': ['python', '-u', Var('root_dir') + '/sync_chromium.py',
                '--target-revision', Var('chromium_revision')],
   },
   {
     # Create links to shared dependencies in Chromium.
     'name': 'setup_links',
     'pattern': '.',
     'action': ['python', Var('root_dir') + '/setup_links.py'],
   },
   {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
     'pattern': '.',
     'action': ['python', Var('root_dir') + '/gyp_libyuv'],
   },
 ]