Use new sanitizer coverage flags.

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 .pyl, or "Python Literal", file. You can treat it just like a
 # .json file, with the following exceptions:
 # * all keys must be quoted (use single quotes, please);
 # * comments are allowed, using '#' syntax; and
 # * trailing commas are allowed.
 
@@ skipping 1670 matching lines @@
 
     'debug_trybot': {
       'mixins': ['debug_bot', 'minimal_symbols'],
     },
 
     'disable_nacl': {
       'gn_args': 'enable_nacl=false',
     },
 
     'edge': {
-      'gn_args': 'sanitizer_coverage_flags="edge"',
+      'gn_args': 'sanitizer_coverage_flags="trace-pc-guard"',
     },
 
     # This mixin is used to force configs that use it to fail. It
     # is used in two cases: when we have bots that we haven't looked
     # at yet and don't know whether they need MB or not, and for bots
     # that are test-only and should never run MB.
     'error': {
       'gn_args': 'error',
     },
 
@@ skipping 228 matching lines @@
 
     'x64': {
       'gn_args': 'target_cpu="x64"',
     },
 
     'x86': {
       'gn_args': 'target_cpu="x86"',
     },
   },
 }