Misc fixes for gn builds with VS 2015

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")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/nacl/config.gni")
 import("//build/toolchain/ccache.gni")
 
@@ skipping 735 matching lines @@
 
       # These are variable shadowing warnings that are new in VS2015. We
       # should work through these at some point -- they may be removed from
       # the RTM release in the /W4 set.
       "/wd4456",
       "/wd4457",
       "/wd4458",
       "/wd4459",
     ]
 
+    if (visual_studio_version == "2015") {
+      # VC++ 2015 changes 32-bit size_t truncation warnings from 4244 to 4267.
+      # Example: short TruncTest(size_t x) { return x; }
+      # Since we already disable 4244 we need to disable 4267 during migration.
+      # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
+      cflags += [ "/wd4267" ]
+    }
+
     # VS xtree header file needs to be patched or 4702 (unreachable code
     # warning) is reported if _HAS_EXCEPTIONS=0. Disable the warning if xtree is
     # not patched.
     if (!msvs_xtree_patched &&
         exec_script("../../win_is_xtree_patched.py", [], "value") == 0) {
       cflags += [ "/wd4702" ]  # Unreachable code.
     }
 
     # Building with Clang on Windows is a work in progress and very
     # experimental. See crbug.com/82385.
@@ skipping 542 matching lines @@
   if (symbol_level == 0) {
     configs = [ ":no_symbols" ]
   } else if (symbol_level == 1) {
     configs = [ ":minimal_symbols" ]
   } else if (symbol_level == 2) {
     configs = [ ":symbols" ]
   } else {
     assert(false)
   }
 }