Disable VS 2015 warning that fires on compiler-generated constructors.

build/config/compiler/BUILD.gn

 # Copyright (c) 2013 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/chrome_build.gni")
 if (current_cpu == "arm") {
   import("//build/config/arm.gni")
 }
 if (current_cpu == "mipsel" || current_cpu == "mips64el") {
@@ skipping 734 matching lines @@
     "/wd4355",
 
     # C4503: 'identifier': decorated name length exceeded, name was
     #        truncated
     # This only means that some long error messages might have truncated
     # identifiers in the presence of lots of templates.  It has no effect on
     # program correctness and there's no real reason to waste time trying to
     # prevent it.
     "/wd4503",
 
+    # Warning C4589 says: "Constructor of abstract class ignores
+    # initializer for virtual base class." Disable this warning because it
+    # is flaky in VS 2015 RTM. It triggers on compiler generated
+    # copy-constructors in some cases.
+    "/wd4589",
+
     # C4611: interaction between 'function' and C++ object destruction is
     #        non-portable
     # This warning is unavoidable when using e.g. setjmp/longjmp.  MSDN
     # suggests using exceptions instead of setjmp/longjmp for C++, but
     # Chromium code compiles without exception support.  We therefore have to
     # use setjmp/longjmp for e.g. JPEG decode error handling, which means we
     # have to turn off this warning (and be careful about how object
     # destruction happens in such cases).
     "/wd4611",
 
@@ skipping 470 matching lines @@
       cflags += [ "-gsplit-dwarf" ]
     }
   }
 }
 
 config("no_symbols") {
   if (!is_win) {
     cflags = [ "-g0" ]
   }
 }