Remove a few un-necessary string copies in net/

net/http/http_request_headers.cc

 // 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.
 
 #include "net/http/http_request_headers.h"
 
 #include "base/logging.h"
 #include "base/string_util.h"
 #include "base/stringprintf.h"
 #include "base/strings/string_split.h"
@@ skipping 67 matching lines @@
 }
 
 void HttpRequestHeaders::Clear() {
   headers_.clear();
 }
 
 void HttpRequestHeaders::SetHeader(const base::StringPiece& key,
                                    const base::StringPiece& value) {
   HeaderVector::iterator it = FindHeader(key);
   if (it != headers_.end())
-    it->value = value.as_string();
+    it->value.assign(value.data(), value.size());
   else
-    headers_.push_back(HeaderKeyValuePair(key.as_string(), value.as_string()));
+    headers_.push_back(HeaderKeyValuePair(key, value));
 }
 
 void HttpRequestHeaders::SetHeaderIfMissing(const base::StringPiece& key,
                                             const base::StringPiece& value) {
   HeaderVector::iterator it = FindHeader(key);
   if (it == headers_.end())
-    headers_.push_back(HeaderKeyValuePair(key.as_string(), value.as_string()));
+    headers_.push_back(HeaderKeyValuePair(key, value));
 }
 
 void HttpRequestHeaders::RemoveHeader(const base::StringPiece& key) {
   HeaderVector::iterator it = FindHeader(key);
   if (it != headers_.end())
     headers_.erase(it);
 }
 
 void HttpRequestHeaders::AddHeaderFromString(
     const base::StringPiece& header_line) {
@@ skipping 141 matching lines @@
        it != headers_.end(); ++it) {
     if (key.length() == it->key.length() &&
         !base::strncasecmp(key.data(), it->key.data(), key.length()))
       return it;
   }
 
   return headers_.end();
 }
 
 }  // namespace net