Mac OS X build: turn off common word macros in AssertMacros.h

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 4000efe768d7df16aef16cb3402652c9fd1f45d8..58fcbcb32e94b5c833e3e5538ca051ca67336b97 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -4521,6 +4521,13 @@
     }],  # OS=="mac" or OS=="ios"
     ['OS=="mac"', {
       'target_defaults': {
+        'defines': [
+          # Prevent Mac OS X AssertMacros.h from defining macros that collide
+          # with common names, like 'check', 'require', and 'verify'.
+          # (Included by system header. Also exists on iOS but not included.)
+          # http://opensource.apple.com/source/CarbonHeaders/CarbonHeaders-18.1/AssertMacros.h
+          '__ASSERT_MACROS_DEFINE_VERSIONS_WITHOUT_UNDERSCORE=0',
+        ],
         'variables': {
           # These should end with %, but there seems to be a bug with % in
           # variables that are intended to be set to different values in