Prevent spurious warning during the android build.

build/android/gyp/util/build_utils.py

Index: build/android/gyp/util/build_utils.py
diff --git a/build/android/gyp/util/build_utils.py b/build/android/gyp/util/build_utils.py
index aa0b8ec4dcda4bffd8ef60a854959b690c344460..65b1a643c26a2ca920ff176af40bfcad85057f3d 100644
--- a/build/android/gyp/util/build_utils.py
+++ b/build/android/gyp/util/build_utils.py
@@ -236,6 +236,7 @@ def ZipDir(output, base_dir):
 
 
 def MergeZips(output, inputs, exclude_patterns=None):
+  added_names = set()
   def Allow(name):
     if exclude_patterns is not None:
       for p in exclude_patterns:
@@ -247,8 +248,9 @@ def MergeZips(output, inputs, exclude_patterns=None):
     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):