Laying the groundwork for targeting WinRT for WebRTC.

Now supporting various flavors of WinRT in the target_os argument.
Setting compiler and linker flags so cc files are compiled
to support C++/CX syntax.

This is part of a larger effort to port WebRTC to WinRT.

Review URL: https://codereview.chromium.org/1150183009

Cr-Original-Commit-Position: refs/heads/master@{#340893}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 56f81e32556d513af513eac0710f2e85877ffa3b

config/BUILDCONFIG.gn

@@ -173,7 +173,8 @@ declare_args() {
 # aix or one of the BSDs. If you need to check these, just check the
 # current_os value directly.
 
-if (current_os == "win") {
+if (current_os == "win" || current_os == "winrt_81" ||
+    current_os == "winrt_81_phone" || current_os == "winrt_10") {
   is_android = false
   is_chromeos = false
   is_ios = false
@@ -393,6 +394,10 @@ if (is_win) {
     "//build/config/win:winver",
   ]
 }
+if (current_os == "winrt_81" || current_os == "winrt_81_phone" ||
+    current_os == "winrt_10") {
+  _native_compiler_configs += [ "//build/config/win:target_winrt" ]
+}
 if (is_posix) {
   _native_compiler_configs += [
     "//build/config/gcc:no_exceptions",
@@ -548,7 +553,14 @@ if (is_win) {
   } else {
     host_toolchain = "//build/toolchain/win:$current_cpu"
   }
+
+  if (current_os == "win") {
     set_default_toolchain("$host_toolchain")
+  } else if (current_cpu == "x64") {  # WinRT x64
+    set_default_toolchain("//build/toolchain/win:winrt_x64")
+  } else if (current_cpu == "x86") {  # WinRT x86
+    set_default_toolchain("//build/toolchain/win:winrt_x86")
+  }
 } else if (is_android) {
   if (host_os == "linux") {
     # Use clang for the x86/64 Linux host builds.

config/compiler/BUILD.gn

@@ -622,8 +622,15 @@ config("runtime_library") {
       }
     }
   } else {
-    # Static CRT.
-    if (is_win) {
+    if (is_win && current_os != "win") {
+      # WindowsRT: use the dynamic CRT.
+      if (is_debug) {
+        cflags += [ "/MDd" ]
+      } else {
+        cflags += [ "/MD" ]
+      }
+    } else if (is_win) {
+      # Desktop Windows: static CRT.
       if (is_debug) {
         cflags += [ "/MTd" ]
       } else {

config/win/BUILD.gn

@@ -180,3 +180,18 @@ config("lean_and_mean") {
 config("nominmax") {
   defines = [ "NOMINMAX" ]
 }
+
+# Target WinRT ----------------------------------------------------------------
+
+# When targeting Windows Runtime, certain compiler/linker flags are necessary.
+
+config("target_winrt") {
+  defines = [
+    "WINRT",
+    "WINAPI_FAMILY=WINAPI_FAMILY_PC_APP",
+  ]
+  cflags_cc = [
+    "/ZW",
+    "/EHsc",
+  ]
+}

toolchain/win/BUILD.gn

@@ -50,6 +50,7 @@ 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)) {
@@ -206,6 +207,7 @@ template("msvc_toolchain") {
       if (defined(invoker.is_clang)) {
         is_clang = invoker.is_clang
       }
+      current_os = invoker.current_os
     }
   }
 }
@@ -227,6 +229,7 @@ if (current_cpu == "x86") {
     prefix = rebase_path("//third_party/llvm-build/Release+Asserts/bin",
                          root_build_dir)
     cl = "${goma_prefix}$prefix/clang-cl.exe"
+    current_os = "win"
     is_clang = true
   }
 }
@@ -244,6 +247,26 @@ if (current_cpu == "x64") {
     prefix = rebase_path("//third_party/llvm-build/Release+Asserts/bin",
                          root_build_dir)
     cl = "${goma_prefix}$prefix/clang-cl.exe"
+    current_os = "win"
     is_clang = true
   }
 }
+
+# WinRT toolchains
+msvc_toolchain("winrt_x86") {
+  environment = "environment.winrt_x86"
+  cl = "${goma_prefix}\"${vc_bin_dir}/cl.exe\""
+  is_clang = false
+
+  current_cpu = "x86"
+  current_os = current_os
+}
+
+msvc_toolchain("winrt_x64") {
+  environment = "environment.winrt_x64"
+  cl = "${goma_prefix}\"${vc_bin_dir}/cl.exe\""
+  is_clang = false
+
+  current_cpu = "x64"
+  current_os = current_os
+}

toolchain/win/setup_toolchain.py

@@ -146,6 +146,15 @@ def main():
     with open('environment.' + cpu, 'wb') as f:
       f.write(env_block)
 
+    # Create a store app version of the environment.
+    if 'LIB' in env:
+      env['LIB']     = env['LIB']    .replace(r'\VC\LIB', r'\VC\LIB\STORE')
+    if 'LIBPATH' in env:
+      env['LIBPATH'] = env['LIBPATH'].replace(r'\VC\LIB', r'\VC\LIB\STORE')
+    env_block = _FormatAsEnvironmentBlock(env)
+    with open('environment.winrt_' + cpu, 'wb') as f:
+        f.write(env_block)
+
   assert vc_bin_dir
   print 'vc_bin_dir = "%s"' % vc_bin_dir