Laying the groundwork for targeting WinRT.

build/toolchain/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.
 
 declare_args() {
   # Path to the directory containing the VC binaries for the right
   # combination of host and target architectures. Currently only the
   # 64-bit host toolchain is supported, with either 32-bit or 64-bit targets.
   # If vc_bin_dir is not specified on the command line (and it normally
   # isn't), we will dynamically determine the right value to use at runtime.
@@ skipping 26 matching lines @@
 
 if (vc_bin_dir == "") {
   vc_bin_dir = toolchain_data.vc_bin_dir
 }
 
 # This value will be inherited in the toolchain below.
 concurrent_links = exec_script("../get_concurrent_links.py", [], "value")
 
 # Parameters:
 #  current_cpu: current_cpu to pass as a build arg
+#  current_os: current_os to pass as a build arg
 #  environment: File name of environment file.
 template("msvc_toolchain") {
   if (defined(invoker.concurrent_links)) {
     concurrent_links = invoker.concurrent_links
   }
 
   env = invoker.environment
 
   if (is_debug) {
     configuration = "Debug"
@@ skipping 137 matching lines @@
     tool("copy") {
       command =
           "$python_path gyp-win-tool recursive-mirror {{source}} {{output}}"
       description = "COPY {{source}} {{output}}"
     }
 
     # When invoking this toolchain not as the default one, these args will be
     # passed to the build. They are ignored when this is the default toolchain.
     toolchain_args() {
       current_cpu = invoker.current_cpu
+      current_os = invoker.current_os
     }
   }
 }
 
 # TODO(dpranke): Declare both toolchains all of the time when we
 # get it sorted out how we want to support them both in a single build.
 # Right now only one of these can be enabled at a time because the
 # runtime libraries get copied to root_build_dir and would collide.
 if (current_cpu == "x86") {
   msvc_toolchain("32") {
     environment = "environment.x86"
 
     current_cpu = "x86"
+    current_os = "win"
   }
 }
 
 if (current_cpu == "x64") {
   msvc_toolchain("64") {
     environment = "environment.x64"
 
     current_cpu = "x64"
+    current_os = "win"
   }
 }
+
+if (current_os != "win") {  # WinRT toolchains
+  if (current_cpu == "x86") {

[brettw, 2015/07/22 20:29:20]

You can delete the two inner conditions. You can define as many toolchains as
you want. I realize the code above this does the same thing but that should be
fixed at some point (you don't have to).

+    msvc_toolchain("winrt_x86") {
+      environment = "environment.winrt_x86"
+
+      current_cpu = "x86"
+      current_os = current_os
+    }
+  }
+
+  if (current_cpu == "x64") {
+    msvc_toolchain("winrt_x64") {
+      environment = "environment.winrt_x64"
+
+      current_cpu = "x64"
+      current_os = current_os
+    }
+  }
+}