Revert of Handle unpatched VS xtree header

build/config/compiler/BUILD.gn

Index: build/config/compiler/BUILD.gn
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index 1324c3a618064c516f2116645573ead46e759729..5cf0331c87d64bb16123d72e0993db9c448424b1 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -48,13 +48,6 @@
   # http://gcc.gnu.org/wiki/DebugFission
   use_debug_fission =
       !is_win && use_gold && linux_use_bundled_binutils && !use_ccache
-
-  if (is_win) {
-    # Whether the VS xtree header has been patched to disable warning 4702. If
-    # it has, then we don't need to disable 4702 (unreachable code warning).
-    # The patch is preapplied to the internal toolchain and hence all bots.
-    msvs_xtree_patched = false
-  }
 }
 
 # default_include_dirs ---------------------------------------------------------
@@ -782,17 +775,6 @@
       "/wd4610",  # Class can never be instantiated, constructor required.
       "/wd4996",  # Deprecated function warning.
     ]
-
-    # VS xtree header file needs to be patched or 4702 (unreachable code
-    # warning) is reported if _HAS_EXCEPTIONS=0. Disable the warning if xtree is
-    # not patched.
-    if (!msvs_xtree_patched) {
-      if (exec_script("../../win_is_xtree_patched.py", [], "value") == 1) {
-        msvs_xtree_patched = true
-      } else {
-        cflags += [ "/wd4702" ]  # Unreachable code.
-      }
-    }
   } else {
     # Common GCC warning setup.
     cflags = [