Disable a warning in the GN build.

Source/BUILD.gn

 # Copyright 2014 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.
 
 import("config.gni")
 if (is_clang) {
   import("//build/config/clang/clang.gni")
 }
 
 # features ---------------------------------------------------------------------
@@ skipping 17 matching lines @@
   include_dirs = [ ".", ".." ]
 
   cflags = []
   defines = []
 
   if (is_win) {
     cflags += [
       "/wd4305",  # Truncation from 'type1' to 'type2'.
       "/wd4324",  # Struct padded due to declspec(align).
       "/wd4714",  # Function marked forceinline not inlined.
+      "/wd4800",  # Value forced to bool.
       "/wd4996",  # Deprecated function call.
     ]
   }
 
   if (is_win) {
     if (component_mode == "shared_library") {
       defines += [ "USING_V8_SHARED" ]
     }
   } else {  # ! Windows
     # TODO(GYP) this should be based on gcc_version >= 46 but GN doesn't have a
@@ skipping 19 matching lines @@
   }
 }
 
 # stubs ------------------------------------------------------------------------
 
 # These set up include paths for targets that haven't been converted yet. They
 # can be removed when the corresponding targets have been converted to GN.
 config("npapi_stub") {
   include_dirs = [ "//third_party/npapi", "//third_party/npapi/bindings" ]
 }