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

base/string_piece.cc

Index: base/string_piece.cc
diff --git a/base/string_piece.cc b/base/string_piece.cc
index 27f00136c2e3414fbd12342604d68dc0526ffa5e..7a41361bb606b9e8fb6e796b19cba8ca84d4656e 100644
--- a/base/string_piece.cc
+++ b/base/string_piece.cc
@@ -1,4 +1,4 @@
-// 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.cc with modifications
@@ -27,6 +27,11 @@ bool operator==(const StringPiece& x, const StringPiece& y) {
   return StringPiece::wordmemcmp(x.data(), y.data(), x.size()) == 0;
 }
 
+std::ostream& operator<<(std::ostream& o, const StringPiece& piece) {
+  o.write(piece.data(), static_cast<std::streamsize>(piece.size()));
+  return o;
+}
+
 namespace internal {
 void CopyToString(const StringPiece& self, std::string* target) {
   target->assign(!self.empty() ? self.data() : "", self.size());