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

build/common.gypi

 # Copyright (c) 2012 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 5593 matching lines @@
           4355,
 
           # 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.
           4503,
 
+          # 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.
+          4589,
+
           # 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).
           4611,
 
@@ skipping 580 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }