Remove mojo/tools/, not needed in chromium

mojo/mojo_base.gyp

Index: mojo/mojo_base.gyp
diff --git a/mojo/mojo_base.gyp b/mojo/mojo_base.gyp
index 315bea04ae310b021bc6ff8186447d8ae131be3b..72c89b3d409b19c36eac7bb8cae0f129ba90e1ae 100644
--- a/mojo/mojo_base.gyp
+++ b/mojo/mojo_base.gyp
@@ -21,7 +21,6 @@
         # to be built.
         'mojo_common_lib',
         'mojo_common_unittests',
-        'mojo_message_generator',
       ],
       'conditions': [
         ['OS == "android"', {
@@ -186,22 +185,6 @@
         'bindings/js/waiting_callback.h',
       ],
     },
-    {
-      # GN version: //mojo/tools:message_generator
-      'target_name': 'mojo_message_generator',
-      'type': 'executable',
-      'dependencies': [
-        '../base/base.gyp:base',
-        '../testing/gtest.gyp:gtest',
-        'edk/mojo_edk.gyp:mojo_system_impl',
-        'mojo_common_lib',
-        'mojo_environment_chromium',
-        'public/mojo_public.gyp:mojo_cpp_bindings',
-      ],
-      'sources': [
-        'tools/message_generator.cc',
-      ],
-    },
   ],
   'conditions': [
     ['OS=="android"', {