Make *some* version of the Win GN build work.

third_party/zlib/BUILD.gn

Index: third_party/zlib/BUILD.gn
diff --git a/third_party/zlib/BUILD.gn b/third_party/zlib/BUILD.gn
index 18cf816397c05839f3f2d76f981fa95e0ee42a36..5dbec0ff6bf3cad30fdaf8f240a3ba92464ef392 100644
--- a/third_party/zlib/BUILD.gn
+++ b/third_party/zlib/BUILD.gn
@@ -7,11 +7,15 @@ config("zlib_config") {
 }
 
 static_library("zlib_x86_simd") {
-  if (cpu_arch == "x86" || cpu_arch == "x64") {
+  if (!is_win && (cpu_arch == "x86" || cpu_arch == "x64")) {

[Nico, 2014/11/18 19:13:43]

This isn't correct. The gyp version does use crc_folder.c and fill_window_sse.c
on Windows, it just doesn't need the -msse4.2 flags and whatnot.

[Dirk Pranke, 2014/11/18 20:37:45]

Okay, good to know. I'll try to fix that in a follow up patch.

I fully expect many of these initial patches to be wrong in some dimension;
often we're just trying to get things to compile *at all*, and we'll have to go
and patch things later.

This is not to say that we shouldn't try to get things right from the start,
just that we won't always be successful.

     sources = [ "crc_folding.c", "fill_window_sse.c" ]
     cflags = [ "-msse2", "-msse4.2", "-mpclmul" ]
   } else {
     sources = [ "simd_stub.c"]
+    if (is_win) {
+      # TODO(GYP): crbug.com/431462 disable warning about structure padding.
+      cflags = [ "/wd4324" ]
+    }
   }
 }
 
@@ -52,7 +56,7 @@ static_library("zlib") {
     "zutil.h",
   ]
 
-  if (cpu_arch == "x86" || cpu_arch == "x64") {
+  if (!is_win && (cpu_arch == "x86" || cpu_arch == "x64")) {
     sources += [ "x86.c" ]
   }