WebRTC: Add Linux 32-bit trybots

masters/master.tryserver.webrtc/slaves.cfg

 # 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.
 
 slaves = [
   # Linux.
   {
     'master': 'WebRTCTryServer',
     'os': 'linux',
     'version': 'trusty',
     'bits': '64',
     'builder': [
       'android_clang_dbg',
       'android_compile_dbg',
       'android_compile_rel',
       'android_compile_arm64_dbg',
       'android_compile_arm64_rel',
       'android_compile_mips_dbg',
       'android_compile_x86_rel',
       'android_compile_x86_dbg',
       'android_compile_x64_dbg',
       'android_gyp_dbg',
       'android_gyp_rel',
       'linux_compile_dbg',
       'linux_compile_rel',
       'linux_dbg',
       'linux_rel',
+      'linux32_dbg',
+      'linux32_rel',
       'linux_gyp_dbg',
       'linux_gyp_rel',
       'linux_libfuzzer_rel',
       'linux_arm',
       'linux_asan',
       'linux_memcheck',
       'linux_msan',
       'linux_swarming',
       'linux_tsan2',
       'linux_ubsan',
@@ skipping 147 matching lines @@
     'master': 'WebRTCTryServer',
     'os': 'win',
     'version': 'win7',
     'bits': '64',
     'builder': [
       'win_baremetal',
     ],
     'hostname': hostname,
   } for hostname in ['build143-b4', 'build139-b4']
 ]