Move operator<< for StringPiece into string_piece.{h,cc}

base/string_piece.h

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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.
 // Copied from strings/stringpiece.h with modifications
 //
 // A string-like object that points to a sized piece of memory.
 //
 // Functions or methods may use const StringPiece& parameters to accept either
 // a "const char*" or a "string" value that will be implicitly converted to
 // a StringPiece.  The implicit conversion means that it is often appropriate
 // to include this .h file in other files rather than forward-declaring
 // StringPiece as would be appropriate for most other Google classes.
 //
 // Systematic usage of StringPiece is encouraged as it will reduce unnecessary
 // conversions from "const char*" to "string" and back again.
 //
 // StringPiece16 is similar to StringPiece but for base::string16 instead of
 // std::string. We do not define as large of a subset of the STL functions
 // from basic_string as in StringPiece, but this can be changed if these
 // functions (find, find_first_of, etc.) are found to be useful in this context.
 //
 
 #ifndef BASE_STRING_PIECE_H_
 #define BASE_STRING_PIECE_H_
 #pragma once
 
+#include <iosfwd>
 #include <string>
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
 #include "base/hash_tables.h"
 #include "base/string16.h"
 
 namespace base {
 
 template <typename STRING_TYPE> class BasicStringPiece;
@@ skipping 355 matching lines @@
 }
 
 inline bool operator<=(const StringPiece16& x, const StringPiece16& y) {
   return !(x > y);
 }
 
 inline bool operator>=(const StringPiece16& x, const StringPiece16& y) {
   return !(x < y);
 }
 
+BASE_EXPORT std::ostream& operator<<(std::ostream& o,
+                                     const StringPiece& piece);
+
 }  // namespace base
 
 // We provide appropriate hash functions so StringPiece and StringPiece16 can
 // be used as keys in hash sets and maps.
 
 // This hash function is copied from base/hash_tables.h. We don't use the
 // ones already defined for string and string16 directly because it would
 // require the string constructors to be called, which we don't want.
 #define HASH_STRING_PIECE(StringPieceType, string_piece)                \
   std::size_t result = 0;                                               \
@@ skipping 25 matching lines @@
 }
 inline size_t hash_value(const base::StringPiece16& sp16) {
   HASH_STRING_PIECE(base::StringPiece16, sp16);
 }
 
 #endif  // COMPILER
 
 }  // namespace BASE_HASH_NAMESPACE
 
 #endif  // BASE_STRING_PIECE_H_