[Cast] Consolidate plethora of GYP files into cast.gyp and cast_testing.gypi.

media/cast/rtp_receiver/rtp_receiver.gyp

-# 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.
-
-{
-  'variables': {
-    'chromium_code': 1,
-  },
-  'targets': [
-    {
-      'target_name': 'cast_rtp_receiver',
-      'type': 'static_library',
-      'include_dirs': [
-        '<(DEPTH)/',
-        '<(DEPTH)/third_party/',
-      ],
-      'sources': [
-        'receiver_stats.cc',
-        'receiver_stats.h',
-        'rtp_receiver.cc',
-        'rtp_receiver.h',
-      ], # source
-      'dependencies': [
-        '<(DEPTH)/base/base.gyp:base',
-        '<(DEPTH)/media/cast/transport/cast_transport.gyp:cast_transport',
-        'rtp_parser/rtp_parser.gyp:*',
-      ],
-    },
-  ],
-}