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

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 989fb18c08502491d42ed6accbfddab6defe8b83..f6c4cd0df21b4ebc9eeaee0dfc2158bd8c659b57 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -5653,6 +5653,18 @@
           # See http://bugs.icu-project.org/trac/ticket/11122
           4595,
         ],
+        'conditions': [
+          ['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
+            ],
+          }],
+        ],
         'msvs_settings': {
           'VCCLCompilerTool': {
             'AdditionalOptions': ['/MP'],