Remove libvpx from FFmpeg in favour of ffvp8.

libvpx/libvpx.gyp

 # Copyright (c) 2011 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': {
     # Generic libvpx C sources for both x86 and ARM targets.
     'libvpx_generic_sources': [
       'source/libvpx/vp8/common/alloccommon.c',
       'source/libvpx/vp8/common/blockd.c',
       'source/libvpx/vp8/common/debugmodes.c',
@@ skipping 125 matching lines @@
           'dependencies': [
             '../yasm/yasm.gyp:yasm#host',
           ],
           'include_dirs': [
             'source/config/<(OS)/<(target_arch)',
             'source/libvpx',
             'source/libvpx/vp8/common',
             'source/libvpx/vp8/decoder',
             'source/libvpx/vp8/encoder',
           ],
+          'direct_dependent_settings': {
+            'include_dirs': [
+              'source/libvpx',
+            ],
+          },
           'cflags!': [
             # Ensure the symbols are exported since this library gets wrapped by
             # ffmpeg's shared lib.  When we stop doing that (crbug.com/70687)
             # this can go away.
             '-fvisibility=hidden',
           ],
           'conditions': [
             [ 'OS=="mac"', {
               'xcode_settings': {
                 'GCC_SYMBOLS_PRIVATE_EXTERN': 'NO',  # No -fvisibility=hidden
@@ skipping 372 matching lines @@
       },
     },
   ],
 }
 
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