Update from https://crrev.com/304121

third_party/zlib/zlib.gyp

Index: third_party/zlib/zlib.gyp
diff --git a/third_party/zlib/zlib.gyp b/third_party/zlib/zlib.gyp
index 8c5ae44b9b99501f01003318bc74229b1e07b1df..22a48a3ce4f6d3f33d9016125c7af15fac06ebb0 100644
--- a/third_party/zlib/zlib.gyp
+++ b/third_party/zlib/zlib.gyp
@@ -8,9 +8,11 @@
       'target_name' : 'zlib_x86_simd',
       'type': 'static_library',
       'conditions': [
-        # See http://crbug.com/420616 gyp on mac & ios doesn't apply cflags
-        ['OS!="ios" and OS!="mac" and (target_arch=="ia32" or target_arch=="x64")', {
+        ['OS!="ios" and (target_arch=="ia32" or target_arch=="x64")', {
           'cflags' : ["-msse2", "-msse4.2", "-mpclmul"],
+          'xcode_settings' : {
+             'OTHER_CFLAGS' : ["-msse4.2", "-mpclmul"],
+          },
           'sources' : [ 'crc_folding.c',
                         'fill_window_sse.c']
         }, {
@@ -65,7 +67,7 @@
         ],
       },
       'conditions': [
-        ['OS!="ios" and OS!="mac" and (target_arch=="ia32" or target_arch=="x64")', {
+        ['OS!="ios" and (target_arch=="ia32" or target_arch=="x64")', {
           'sources' : [ 'x86.c', ],
         }],
         ['OS!="win"', {