Move mojo gypfiles to toplevel mojo

mojo/mojom_bindings_generator_explicit.gypi

 # Copyright 2013 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.
 
 {
   'includes': [
     'mojom_bindings_generator_variables.gypi',
   ],
   'variables': {
     'mojom_base_output_dir':
@@ skipping 60 matching lines @@
         '<(SHARED_INTERMEDIATE_DIR)',
       ],
       'variables': {
         'generated_src_dirs': [
           '<(PRODUCT_DIR)/java_mojo/<(_target_name)/src',
         ],
       },
     }
   },
 }