Cleanup: Pass std::string as const reference from content/

content/browser/indexed_db/indexed_db_leveldb_coding_unittest.cc

 // Copyright (c) 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.
 
 #include "content/browser/indexed_db/indexed_db_leveldb_coding.h"
 
 #include <limits>
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 458 matching lines @@
     std::string encoded_b = WrappedEncodeStringWithLength(b);
     EXPECT_TRUE(encoded_a.size());
 
     EXPECT_LT(CompareStrings(encoded_a, encoded_b), 0);
     EXPECT_GT(CompareStrings(encoded_b, encoded_a), 0);
     EXPECT_EQ(CompareStrings(encoded_a, encoded_a), 0);
     EXPECT_EQ(CompareStrings(encoded_b, encoded_b), 0);
   }
 }
 
-static std::string WrappedEncodeBinary(std::string value) {
+static std::string WrappedEncodeBinary(const std::string& value) {
   std::string buffer;
   EncodeBinary(value, &buffer);
   return buffer;
 }
 
 TEST(IndexedDBLevelDBCodingTest, EncodeBinary) {
   const unsigned char binary_data[] = {0x00, 0x01, 0xfe, 0xff};
   EXPECT_EQ(
       1u,
       WrappedEncodeBinary(std::string(binary_data, binary_data + 0)).size());
@@ skipping 485 matching lines @@
     std::string b = WrappedEncodeVarInt(static_cast<int64>(n));
 
     EXPECT_EQ(a.size(), b.size());
     EXPECT_EQ(*a.begin(), *b.begin());
   }
 }
 
 }  // namespace
 
 }  // namespace content