Enable Widevine CDM on Linux x64 builds.

third_party/widevine/cdm/widevine_cdm.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': {
     'widevine_cdm_version_h_file%': 'widevine_cdm_version.h',
     'widevine_cdm_binary_files%': [],
     'conditions': [
       [ 'branding == "Chrome"', {
@@ skipping 54 matching lines @@
               'type': 'loadable_module',
               # Allow the plugin wrapper to find the CDM in the same directory.
               'ldflags': ['-Wl,-rpath=\$$ORIGIN'],
             }],
             [ 'chromeos == 1 and target_arch == "arm"', {
               'libraries': [
                 # Copied by widevine_cdm_binaries.
                 '<(PRODUCT_DIR)/libwidevinecdm.so',
               ],
             }],
+            [ 'OS == "linux" and target_arch == "x64"', {
+              'libraries': [
+                # Copied by widevine_cdm_binaries.
+                '<(PRODUCT_DIR)/libwidevinecdm.so',
+              ],
+            }],
             [ 'OS == "win" and 0', {
               'type': 'shared_library',
             }],
             [ 'OS == "mac" and 0', {
               'type': 'loadable_module',
               'mac_bundle': 1,
               'product_extension': 'plugin',
               'xcode_settings': {
                 'OTHER_LDFLAGS': [
                   # Not to strip important symbols by -Wl,-dead_strip.
@@ skipping 19 matching lines @@
       'type': 'none',
       'copies': [{
         # TODO(ddorwin): Do we need a sub-directory? We either need a
         # sub-directory or to rename manifest.json before we can copy it.
         'destination': '<(PRODUCT_DIR)',
         'files': [ '<@(widevine_cdm_binary_files)' ],
       }],
     },
   ],
 }