Add mb config for new WinClang64 (dbg) main waterfall bot.

tools/mb/mb_config.pyl

 # Copyright 2015 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.
 
 {
   # This is a map of buildbot master names -> buildbot builder names ->
   # config names (where each config name is a key in the 'configs' dict,
   # below). MB uses this dict to look up which config to use for a given bot.
   'masters': {
     # Take care when changing any of these builders to ensure that you do not
@@ skipping 196 matching lines @@
       'Site Isolation Linux': 'gn_release_trybot',
       'Site Isolation Win': 'gyp_release_trybot_x64',
       'Vista Tests (dbg)(1)': 'none',
       'Vista Tests (dbg)(2)': 'none',
       'WebKit Linux - TraceWrappables': 'swarming_gn_release_bot_x64',
       'Win LKGR (DrM 64)': 'gn_release_drmemory_drfuzz',
       'Win LKGR (DrM)': 'gn_release_drmemory_drfuzz_x86',
       'Win8 Tests (1)': 'none',
       'Win8 Tests (2)': 'none',
       'WinClang': 'win_clang_debug_bot',
+      'WinClang64 (dbg)': 'win_clang_debug_bot',
       'Windows Browser (DrMemory light) (1)': 'none',
       'Windows Browser (DrMemory light) (2)': 'none',
 
       'Linux Kitchen (kitchen_run)': 'swarming_gn_release_bot',
       'Linux Kitchen (annotated_run)': 'swarming_gn_release_bot',
     },
 
     'chromium.gpu': {
       'Android Debug (Nexus 5)': 'android_gn_debug_static_bot',
       'Android Debug (Nexus 6)': 'android_gn_debug_static_bot',
@@ skipping 1629 matching lines @@
       'gn_args': 'is_component_build=true enable_iterator_debugging=false',
       'gyp_defines': 'component=shared_library build_for_tool=drmemory',
     },
 
     'valgrind': {
       # TODO: add gn_args for 'build_for_tool=memcheck'
       'gyp_defines': 'build_for_tool=memcheck',
     }
   },
 }