Exclude Observatory assets from PRODUCT build dart, dart_precompiled_runtime

tools/gn.py

 #!/usr/bin/env python
 # Copyright 2016 The Dart project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import argparse
 import multiprocessing
 import os
 import shutil
 import subprocess
@@ skipping 171 matching lines @@
       raise Exception("GN support for armv5te unimplemented")
 
   gn_args['is_debug'] = mode == 'debug'
   gn_args['is_release'] = mode == 'release'
   gn_args['is_product'] = mode == 'product'
   gn_args['dart_debug'] = mode == 'debug'
 
   # This setting is only meaningful for Flutter. Standalone builds of the VM
   # should leave this set to 'develop', which causes the build to defer to
   # 'is_debug', 'is_release' and 'is_product'.
-  gn_args['dart_runtime_mode'] = 'develop'
+  if mode == 'product':
+    gn_args['dart_runtime_mode'] = 'release'
+  else:
+    gn_args['dart_runtime_mode'] = 'develop'
 
   dont_use_clang = DontUseClang(args, gn_args['target_os'],
                                       gn_args['host_cpu'],
                                       gn_args['target_cpu'])
   gn_args['is_clang'] = args.clang and not dont_use_clang
 
   gn_args['is_asan'] = args.asan and gn_args['is_clang']
   gn_args['is_msan'] = args.msan and gn_args['is_clang']
   gn_args['is_tsan'] = args.tsan and gn_args['is_clang']
 
@@ skipping 259 matching lines @@
       return 1
 
   endtime = time.time()
   if args.verbose:
     print ("GN Time: %.3f seconds" % (endtime - starttime))
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(Main(sys.argv))