Add "Win asan 64-bit" in order to migrate away from the 2-bit version.

Chromium is thinking to remove the toolchain [1] and WebRTC can
probably switch to run it on x64 without any problem.

[1] - https://groups.google.com/a/chromium.org/d/msg/chromium-dev/IO5v9yx545M/H93qyx3UAgAJ

Bug: webrtc:10696
Change-Id: Ic5c6e795b662319a2338e4c3ff9e190874356296
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/139100
Reviewed-by: Oleh Prypin <oprypin@webrtc.org>
Reviewed-by: Artem Titarenko <artit@webrtc.org>
Commit-Queue: Oleh Prypin <oprypin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28118}
diff --git a/tools_webrtc/mb/mb_config.pyl b/tools_webrtc/mb/mb_config.pyl
index b452f74..026706f 100644
--- a/tools_webrtc/mb/mb_config.pyl
+++ b/tools_webrtc/mb/mb_config.pyl
@@ -92,6 +92,7 @@
       'Win64 Debug (Clang)': 'win_clang_debug_bot_x64',
       'Win64 Release (Clang)': 'win_clang_release_bot_x64',
       'Win32 ASan': 'win_asan_clang_release_bot_x86',
+      'Win64 ASan': 'win_asan_clang_release_bot_x64',
       'Win64 UWP': 'win_uwp_release_bot_x64',
       'Win (more configs)': {
         'bwe_test_logging':
@@ -231,7 +232,7 @@
       'win_x86_clang_rel': 'win_clang_release_bot_x86',
       'win_x64_clang_dbg': 'win_clang_debug_bot_x64',
       'win_x64_clang_rel': 'win_clang_release_bot_x64',
-      'win_asan': 'win_asan_clang_release_bot_x86',
+      'win_asan': 'win_asan_clang_release_bot_x64',
       'win_x64_clang_dbg_win8': 'win_clang_debug_bot_x64',
       'win_x64_clang_dbg_win10': 'win_clang_debug_bot_x64',
       'win_x64_uwp': 'win_uwp_release_bot_x64',
@@ -344,6 +345,10 @@
       'asan', 'clang',  'full_symbols', 'openh264', 'release_bot', 'x86',
       'win_fastlink',
     ],
+    'win_asan_clang_release_bot_x64': [
+      'asan', 'clang',  'full_symbols', 'openh264', 'release_bot', 'x64',
+      'win_fastlink',
+    ],
     'win_uwp_release_bot_x64': [
       # UWP passes compiler flags that are not supported by goma.
       'no_clang', 'openh264', 'x64', 'winuwp', 'release_bot_no_goma'