Remove the build_ffmpegsumo build variable.

build/common.gypi

 # 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 1793 matching lines @@
         # developer builds, to avoid spurious re-linking of native files.
         'optimize_jni_generation%': '<(optimize_jni_generation)',
 
         # Use OpenSSL's struct X509 to represent certificates.
         'use_openssl_certs%': 1,
 
         'proprietary_codecs%': '<(proprietary_codecs)',
         'safe_browsing%': 2,
         'enable_web_speech%': 0,
         'java_bridge%': 1,
-        'build_ffmpegsumo%': 0,
         'use_allocator%': 'none',
 
         # Disable Native Client.
         'disable_nacl%': 1,
 
         # Android does not support background apps.
         'enable_background%': 0,
 
         # Sessions are store separately in the Java side.
         'enable_session_service%': 0,
@@ skipping 4374 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }