Revert of win: Remove unneeded references to visual_studio_version now that it's always 2015.

build/config/win/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/clang/clang.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/win/visual_studio_version.gni")
 import("//build/toolchain/toolchain.gni")
 
@@ skipping 30 matching lines @@
     "/FS",  # Preserve previous PDB behavior.
     "/bigobj",  # Some of our files are bigger than the regular limits.
   ]
 
   # Force C/C++ mode for the given GN detected file type. This is necessary
   # for precompiled headers where the same source file is compiled in both
   # modes.
   cflags_c = [ "/TC" ]
   cflags_cc = [ "/TP" ]
 
-  cflags += [
-    # Tell the compiler to crash on failures. This is undocumented
-    # and unsupported but very handy.
-    "/d2FastFail",
+  # Flags not supported in version 2013.
+  if (visual_studio_version != "2013" && visual_studio_version != "2013e") {
+    cflags += [
+      # Tell the compiler to crash on failures. This is undocumented
+      # and unsupported but very handy.
+      "/d2FastFail",
+    ]
+  }
 
-    # Work around crbug.com/526851, bug in VS 2015 RTM compiler.
-    "/Zc:sizedDealloc-",
+  if (visual_studio_version == "2015") {
+    cflags += [
+      # Work around crbug.com/526851, bug in VS 2015 RTM compiler.
+      "/Zc:sizedDealloc-",
 
-    # Disable thread-safe statics to avoid overhead and because
-    # they are disabled on other platforms. See crbug.com/587210
-    # and -fno-threadsafe-statics.
-    "/Zc:threadSafeInit-",
-  ]
+      # Disable thread-safe statics to avoid overhead and because
+      # they are disabled on other platforms. See crbug.com/587210
+      # and -fno-threadsafe-statics.
+      "/Zc:threadSafeInit-",
+    ]
+  }
 
   # Building with Clang on Windows is a work in progress and very
   # experimental. See crbug.com/82385.
+  # Keep this in sync with the similar block in build/common.gypi
   if (is_clang) {
-    cflags += [ "-fmsc-version=1900" ]
+    if (visual_studio_version == "2013") {
+      cflags += [ "-fmsc-version=1800" ]
+    } else if (visual_studio_version == "2015") {
+      cflags += [ "-fmsc-version=1900" ]
+    }
 
     if (current_cpu == "x86") {
       cflags += [ "-m32" ]
     } else {
       cflags += [ "-m64" ]
     }
 
     if (exec_script("//build/win/use_ansi_codes.py", [], "trim string") ==
         "True") {
       cflags += [
@@ skipping 344 matching lines @@
 
 # Internal stuff --------------------------------------------------------------
 
 # Config used by the MIDL template to disable warnings.
 config("midl_warnings") {
   if (is_clang) {
     # MIDL generates code like "#endif !_MIDL_USE_GUIDDEF_".
     cflags = [ "-Wno-extra-tokens" ]
   }
 }