Disable warning 4702: Unreachable code for the WPO/PGO builds.

build/common.gypi

 # 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 5528 matching lines @@
             ],
           }],
           ['msvs_xtree_patched!=1', {
             # If xtree hasn't been patched, then we disable C4702. Otherwise,
             # it's enabled. This will generally only be true for system-level
             # installed Express users.
             'msvs_disabled_warnings': [
               4702, # unreachable code
             ],
           }],
+          ['full_wpo_on_official==1', {
+            # Disable Warning 4702 ("Unreachable code") for the WPO/PGO
+            # builds. Probably anything that this would catch that
+            # wouldn't be caught in a normal build isn't going to
+            # actually be a bug, so the incremental value of C4702 for
+            # PGO builds is likely very small.
+            'msvs_disabled_warnings': [
+              4702
+            ],
+          }],
         ],
         # Add extra include directories here that need to be in front of the
         # installed and packaged include directories. This may be needed in
         # order to force a particular SDK version, such as to get VS 2013 to use
         # the Windows 10 SDK. Beware of making the INCLUDE variable excessively
         # long, and be sure to make corresponding changes to
         # build\toolchain\win\setup_toolchain.py
         'msvs_system_include_dirs': [
         ],
         'msvs_cygwin_shell': 0,
@@ skipping 727 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }