Update libvpx.gyp for removed third_party libmkv.

libvpx.gyp

 # Copyright (c) 2012 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': {
     'libvpx_build_vp9%': 1,
     'libvpx_source%': 'source/libvpx',
     'conditions': [
       ['os_posix==1', {
         'asm_obj_extension': 'o',
@@ skipping 163 matching lines @@
                   '-Wno-conversion',
                   # libvpx does `if ((a == b))` in some places.
                   '-Wno-parentheses-equality',
                 ],
               },
               'cflags': [
                 '-Wno-conversion',
                 '-Wno-parentheses-equality',
               ],
             }],
-            ['chromeos == 1', {
-              # ChromeOS needs these files for animated WebM avatars.
-              'sources': [
-                '<(libvpx_source)/third_party/libmkv/EbmlIDs.h',
-                '<(libvpx_source)/third_party/libmkv/EbmlWriter.c',
-                '<(libvpx_source)/third_party/libmkv/EbmlWriter.h',
-              ],
-            }],
           ],
         },
       ],
     },
     ],
     # 'libvpx' target for mips builds.
     [ 'target_arch=="mipsel" ', {
       'targets': [
         {
           # This libvpx target contains both encoder and decoder.
@@ skipping 143 matching lines @@
             ['arm_neon==1', {
               'includes': [
                 'libvpx_srcs_arm_neon.gypi',
               ],
             }],
             ['OS == "android"', {
               'includes': [
                 '../../build/android/cpufeatures.gypi',
               ],
             }],
-            ['chromeos == 1', {
-              # ChromeOS needs these files for animated WebM avatars.
-              'sources': [
-                '<(libvpx_source)/third_party/libmkv/EbmlIDs.h',
-                '<(libvpx_source)/third_party/libmkv/EbmlWriter.c',
-                '<(libvpx_source)/third_party/libmkv/EbmlWriter.h',
-              ],
-            }],
             ['OS == "ios"', {
               'xcode_settings': {
                 'OTHER_CFLAGS!': [
                   # Breaks at least boolhuff_armv5te:token_high_bit_not_set_ev.
                   '-fstack-protector-all',  # Implies -fstack-protector
                 ],
               },
             }],
           ],
         },
@@ skipping 220 matching lines @@
          # Need this otherwise gyp won't run the rule on them.
           'sources': [
             '<(INTERMEDIATE_DIR)/vpx_scale_asm_offsets.o',
           ],
         }],
       ],
       'includes': ['obj_int_extract.gypi'],
     },
   ],
 }