Add support for response filtering (issue #515).

- Add a new CefRequestHandler::GetResourceResponseFilter method and
  CefResponseFilter class.

patch/patch.cfg

@@ -241,4 +241,10 @@ patches = [
     'name': 'pdfium_print_549365',
     'path': '../third_party/pdfium/',
   },
+  {
+    # Enable support for filtering resource responses.
+    # https://bitbucket.org/chromiumembedded/cef/issues/515
+    'name': 'net_filter_515',
+    'path': '../net/',
+  },
 ]