Update Dart dependency and patch dart_controller to account for non-backwards compatible API update

DEPS

 # This file is automatically processed to create .DEPS.git which is the file
 # that gclient uses under git.
 #
 # See http://code.google.com/p/chromium/wiki/UsingGit
 #
 # To test manually, run:
 #   python tools/deps2git/deps2git.py -o .DEPS.git -w <gclientdir>
 # where <gcliendir> is the absolute path to the directory containing the
 # .gclient file (the parent of 'src').
 #
 # Then commit .DEPS.git locally (gclient doesn't like dirty trees) and run
 #   gclient sync
 # Verify the thing happened you wanted. Then revert your .DEPS.git change
 # DO NOT CHECK IN CHANGES TO .DEPS.git upstream. It will be automatically
 # updated by a bot when you modify this one.
 #
 # When adding a new dependency, please update the top-level .gitignore file
 # to list the dependency's destination directory.
 
 vars = {
   'chromium_git': 'https://chromium.googlesource.com',
   'dart_svn': 'https://dart.googlecode.com',
   'skia_revision': '409fd66a5afcef5f165f7ccec7c3473add231752',
   'v8_revision': '230d131d173ab2d60291d303177bc04ec3f6e519',
   'angle_revision': 'bdd419f9f5b006e913606e7363125942c8ae06bc',
   'buildtools_revision': 'fa660d47fa1a6c649d5c29e001348447c55709e6',
-  'dart_revision': '856248f1356d1e7564c8b27dcbe35c770cde2eb5',
+  'dart_revision': '7c1bccb26325d26b62324e5780eca1d13e98ccc4',
   'dart_observatory_packages_revision': '45565',
   'pdfium_revision': 'b0115665b0f33971f1b7077740d51e155583cec0',
   'boringssl_revision': '642f1498d056dbba3e50ed5a232ab2f482626dec',
   'lss_revision': 'e079768b7e3a94dcbe7d338496c0c3bde7151b6e',
   'nss_revision': 'bb4e75a43d007518ae7d618665ea2f25b0c60b63',
   'nacl_revision': '87d5dd90911a0657c27574f78e86b7dfc4ad8b29',
   'vector_math_dart_revision': '65915583f7aa606cb47ed265f853c18c60102b81',
   'box2d_dart_revision': 'c5e65d9546275e78ad2a1d51b459e7638f6e4323',
 }
 
@@ skipping 322 matching lines @@
     'name': 'keyboard_native_resources',
     'pattern': '',
     'action': [ 'download_from_google_storage',
                 '--no_resume',
                 '--no_auth',
                 '--bucket', 'mojo/keyboard_native',
                 '-d', 'src/services/keyboard_native/res',
     ],
   },
 ]