[gn] Enable stricter build flags

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("//build/config/android/config.gni")
 import("//build/config/arm.gni")
 import("//build/config/dcheck_always_on.gni")
 import("//build/config/mips.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 
@@ skipping 445 matching lines @@
       "-Wsign-compare",
 
       # TODO(hans): Remove once http://crbug.com/428099 is resolved.
       "-Winconsistent-missing-override",
     ]
     #if (v8_current_cpu == "x64" || v8_current_cpu == "arm64" ||
     #    v8_current_cpu == "mips64el") {
     #  cflags += [ "-Wshorten-64-to-32" ]
     #}
   }
+
+  if (is_win) {
+    cflags += [
+      "/wd4245",  # Conversion with signed/unsigned mismatch.
+      "/wd4267",  # Conversion with possible loss of data.
+      "/wd4324",  # Padding structure due to alignment.
+      "/wd4701",  # Potentially uninitialized local variable.
+      "/wd4702",  # Unreachable code.
+      "/wd4703",  # Potentially uninitialized local pointer variable.
+      "/wd4709",  # Comma operator within array index expr (bugged).
+      "/wd4718",  # Recursive call has no side-effect.
+      "/wd4800",  # Forcing value to bool.
+    ]
+  }
 }
 
 ###############################################################################
 # Actions
 #
 
 action("js2c") {
   visibility = [ ":*" ]  # Only targets in this file can depend on this.
 
   script = "tools/js2c.py"
@@ skipping 1806 matching lines @@
   defines = []
   deps = [
     ":v8_libbase",
     ":v8_libsampler",
     ":v8_version",
   ]
 
   sources += [ v8_generated_peephole_source ]
   deps += [ ":run_mkpeephole" ]
 
-  if (is_win) {
-    # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
-    cflags = [ "/wd4267" ]
-  }
-
   if (v8_enable_i18n_support) {
     deps += [ "//third_party/icu" ]
     if (is_win) {
       deps += [ "//third_party/icu:icudata" ]
     }
   } else {
     sources -= [
       "src/i18n.cc",
       "src/i18n.h",
     ]
@@ skipping 868 matching lines @@
   ]
 
   configs = [
     ":external_config",
     ":internal_config_base",
   ]
 }
 
 v8_fuzzer("wasm_compile_fuzzer") {
 }