Mojo: Add embedder::PlatformSupport and a simple implementation (and a bit of plumbing).

mojo/mojo_base.gyp

 # 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.
 
 # Essential components (and their tests) that are needed to build
 # Chrome should be here.  Other components that are useful only in
 # Mojo land like mojo_shell should be in mojo.gyp.
 {
   'includes': [
     'mojo_public.gypi',
@@ skipping 91 matching lines @@
         'embedder/platform_channel_pair_win.cc',
         'embedder/platform_channel_utils_posix.cc',
         'embedder/platform_channel_utils_posix.h',
         'embedder/platform_handle.cc',
         'embedder/platform_handle.h',
         'embedder/platform_handle_utils.h',
         'embedder/platform_handle_utils_posix.cc',
         'embedder/platform_handle_utils_win.cc',
         'embedder/platform_handle_vector.h',
         'embedder/platform_shared_buffer.h',
+        'embedder/platform_support.h',
         'embedder/scoped_platform_handle.h',
         'embedder/simple_platform_shared_buffer.cc',
         'embedder/simple_platform_shared_buffer.h',
         'embedder/simple_platform_shared_buffer_posix.cc',
         'embedder/simple_platform_shared_buffer_win.cc',
+        'embedder/simple_platform_support.cc',
+        'embedder/simple_platform_support.h',
         'system/channel.cc',
         'system/channel.h',
         'system/constants.h',
         'system/core.cc',
         'system/core.h',
         'system/data_pipe.cc',
         'system/data_pipe.h',
         'system/data_pipe_consumer_dispatcher.cc',
         'system/data_pipe_consumer_dispatcher.h',
         'system/data_pipe_producer_dispatcher.cc',
@@ skipping 448 matching lines @@
             'mojo_js_unittests.isolate',
           ],
           'sources': [
             'mojo_js_unittests.isolate',
           ],
         },
       ],
     }],
   ]
 }