Misc fixes for gn builds with VS 2015

third_party/leveldatabase/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("//testing/test.gni")
 
 defines = [ "LEVELDB_PLATFORM_CHROMIUM=1" ]
 
 config("leveldatabase_config") {
   include_dirs = [
@@ skipping 264 matching lines @@
 
   test("leveldb_log_test") {
     sources = [
       "src/db/log_test.cc",
     ]
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [ "//build/config/compiler:no_chromium_code" ]
     deps = [
       ":leveldb_testutil",
     ]
+
+    if (is_win) {
+      # db\log_test.cc(486) triggers two warnings:
+      # util\testharness.h(91): warning C4018: '<=': signed/unsigned mismatch
+      # util\testharness.h(89): warning C4018: '>=': signed/unsigned mismatch
+      cflags = [ "/wd4018" ]  # Signed/unsigned mismatch in comparison.
+    }
   }
 
   test("leveldb_skiplist_test") {
     sources = [
       "src/db/skiplist_test.cc",
     ]
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [ "//build/config/compiler:no_chromium_code" ]
     deps = [
       ":leveldb_testutil",
@@ skipping 26 matching lines @@
     sources = [
       "src/db/write_batch_test.cc",
     ]
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [ "//build/config/compiler:no_chromium_code" ]
     deps = [
       ":leveldb_testutil",
     ]
   }
 }