Support google3 DEBUG/NDEBUG handling.

Change-Id: I04beeb6c24969610255d52a1816e444e57dfe51f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/153616
Reviewed-by: Martin Kustermann <kustermann@google.com>
Commit-Queue: David Morgan <davidmorgan@google.com>

Author: davidmorgan

runtime/platform/globals.h

@@ -15,6 +15,14 @@
 #define FALL_THROUGH ((void)0)
 #endif
 
+#if defined(GOOGLE3)
+// google3 builds use NDEBUG to indicate non-debug builds which is different
+// from the way the Dart project expects it: DEBUG indicating a debug build.
+#if !defined(NDEBUG) && !defined(DEBUG)
+#define DEBUG
+#endif  // !NDEBUG && !DEBUG
+#endif  // GOOGLE3
+
 // __STDC_FORMAT_MACROS has to be defined before including <inttypes.h> to
 // enable platform independent printf format specifiers.
 #ifndef __STDC_FORMAT_MACROS