Prevent spurious warning during the android build.

build/android/gyp/util/build_utils.py

 # Copyright 2013 The Chromium 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 ast
 import contextlib
 import fnmatch
 import json
 import os
 import pipes
@@ skipping 218 matching lines @@
   with zipfile.ZipFile(output, 'w') as outfile:
     for root, _, files in os.walk(base_dir):
       for f in files:
         path = os.path.join(root, f)
         archive_path = os.path.relpath(path, base_dir)
         CheckZipPath(archive_path)
         outfile.write(path, archive_path)
 
 
 def MergeZips(output, inputs, exclude_patterns=None):
+  added_names = set()
   def Allow(name):
     if exclude_patterns is not None:
       for p in exclude_patterns:
         if fnmatch.fnmatch(name, p):
           return False
     return True
 
   with zipfile.ZipFile(output, 'w') as out_zip:
     for in_file in inputs:
       with zipfile.ZipFile(in_file, 'r') as in_zip:
         for name in in_zip.namelist():
-          if Allow(name):
+          if name not in added_names and Allow(name):
             out_zip.writestr(name, in_zip.read(name))
+            added_names.add(name)
 
 
 def PrintWarning(message):
   print 'WARNING: ' + message
 
 
 def PrintBigWarning(message):
   print '*****     ' * 8
   PrintWarning(message)
   print '*****     ' * 8
@@ skipping 103 matching lines @@
       file_jsons[file_path] = ReadJson(file_path)
 
     expansion = file_jsons[file_path]
     for k in lookup_path[1:]:
       expansion = expansion[k]
 
     new_args[i] = arg[:match.start()] + str(expansion)
 
   return new_args