Fixes for re-enabling more MSVC level 4 warnings: Source/core/ edition

Source/core/BUILD.gn

Index: Source/core/BUILD.gn
diff --git a/Source/core/BUILD.gn b/Source/core/BUILD.gn
index 3bb3c187f5eaea78b75b420830fff565a69e354b..d7f36969700b7df9bc8241a949fab0a4ffe64153 100644
--- a/Source/core/BUILD.gn
+++ b/Source/core/BUILD.gn
@@ -473,10 +473,11 @@ source_set("core_generated") {
     cflags += [
       # In generated bindings code: "switch contains default but no case".
       # Disable c4267 warnings until we fix size_t to int truncations.
-      # 4702 is disabled because of issues in Bison-generated
+      # 4701 and 4702 are disabled because of issues in Bison-generated
       # XPathGrammar.cpp and CSSGrammar.cpp.
       "/wd4065",
       "/wd4267",
+      "/wd4701",
       "/wd4702",
     ]
   }