Update to Chromium version 68.0.3433.0 (#559327)

Known issues:
- Windows now requires VS 2017 15.7.1 with 10.0.17134.0 SDK.

patch/patch.cfg

@@ -31,6 +31,9 @@ patches = [
     #
     # Write environment.* files with the correct SDK version on Windows.
     # https://bugs.chromium.org/p/chromium/issues/detail?id=634788
+    #
+    # Windows: Add cc_wrapper support for sccache builds.
+    # https://bitbucket.org/chromiumembedded/cef/issues/2432
     'name': 'gn_config',
   },
   {