[android] Override __cxa_demangle() in PRODUCT mode

Saves at least 90KB of binary size.

Change-Id: I9f40cc9fbd3a80421ed5f4b751e47f593cb8d1d5
Reviewed-on: https://dart-review.googlesource.com/11344
Reviewed-by: Siva Annamalai <asiva@google.com>

runtime/vm/native_symbol_android.cc

@@ -10,6 +10,21 @@
 #include <cxxabi.h>  // NOLINT
 #include <dlfcn.h>   // NOLINT
 
+// Even though it's not used in a PRODUCT build, __cxa_demangle() still ends up
+// in the resulting binary for Android. Blowing it away by redefining it like
+// so saves >90KB of binary size.
+#if defined(PRODUCT)
+extern "C" char* __cxa_demangle(const char* mangled_name,
+                                char* buf,
+                                size_t* n,
+                                int* status) {
+  if (status) {
+    *status = -1;
+  }
+  return NULL;
+}
+#endif
+
 namespace dart {
 
 void NativeSymbolResolver::InitOnce() {}