remove libwebm third_party dependency

third_party/libwebm/libwebm.gyp

Index: third_party/libwebm/libwebm.gyp
diff --git a/third_party/libwebm/libwebm.gyp b/third_party/libwebm/libwebm.gyp
deleted file mode 100644
index 2374d675128846df329f6d351c28aab798edc861..0000000000000000000000000000000000000000
--- a/third_party/libwebm/libwebm.gyp
+++ /dev/null
@@ -1,24 +0,0 @@
-# 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.
-
-{
-  'includes': [
-    'libwebm.gypi',
-  ],
-  'targets': [
-    {
-      'target_name': 'libwebm',
-      'type': 'static_library',
-      'sources': [
-        '<@(libwebm_sources)'
-      ],
-      'defines!': [
-        # This macro is declared in common.gypi which causes warning when
-        # compiling mkvmuxerutil.cpp which also defines it.
-        '_CRT_RAND_S',
-      ],
-      'msvs_disabled_warnings': [ 4267 ],
-    },  # target libwebm
-  ]
-}