Mojo JS bindings: flip the default value of use_new_js_bindings to true.

mojo/public/tools/bindings/mojom.gni

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 declare_args() {
   # Indicates whether typemapping should be supported in this build
   # configuration. This may be disabled when building external projects which
   # depend on //mojo but which do not need/want all of the Chromium tree
   # dependencies that come with typemapping.
   #
@@ skipping 131 matching lines @@
 #       TODO(dcheng):
 #           - Convert everything to use OnceCallback.
 #           - Remove support for the old mode.
 #
 #   cpp_only (optional)
 #       If set to true, only the C++ bindings targets will be generated.
 #
 #   use_new_js_bindings (optional)
 #       If set to true, the generated JS code will use the new module loading
 #       approach and the core API exposed by Web IDL.
-#
-#       TODO(yzshen): Switch all existing users to use_new_js_bindings=true and
-#       remove the old mode.
+#       Default value is true.
+#       TODO(yzshen): Convert all users to use new JS bindings and remove the
+#       old mode.
 #
 #   component_output_prefix (optional)
 #       The prefix to use for the output_name of any component library emitted
 #       for generated C++ bindings. If this is omitted, C++ bindings targets are
 #       emitted as source_sets instead. Because this controls the name of the
 #       output shared library binary in the root output directory, it must be
 #       unique across the entire build configuration.
 #
 #       This is required if |component_macro_prefix| is specified.
 #
@@ skipping 453 matching lines @@
               "--export_header",
               invoker.export_header,
             ]
           }
         }
 
         if (!defined(invoker.use_once_callback) || invoker.use_once_callback) {
           args += [ "--use_once_callback" ]
         }
 
-        if (defined(invoker.use_new_js_bindings) &&
+        if (!defined(invoker.use_new_js_bindings) ||
             invoker.use_new_js_bindings) {
           args += [ "--use_new_js_bindings" ]
         }
       }
     }
 
     action(type_mappings_target_name) {
       inputs = _bindings_configuration_files
       outputs = [
         type_mappings_path,
@@ skipping 231 matching lines @@
     forward_variables_from(invoker,
                            "*",
                            [
                              "output_prefix",
                              "macro_prefix",
                            ])
     component_output_prefix = invoker.output_prefix
     component_macro_prefix = invoker.macro_prefix
   }
 }