[url] Reserve size in a smarter way to account for pre-allocated buffers

url/url_util.cc

 // Copyright 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 "url/url_util.h"
 
 #include <stddef.h>
 #include <string.h>
 
 #include "base/debug/leak_annotations.h"
@@ skipping 174 matching lines @@
 }
 
 template <typename CHAR>
 bool DoCanonicalize(const CHAR* spec,
                     int spec_len,
                     bool trim_path_end,
                     WhitespaceRemovalPolicy whitespace_policy,
                     CharsetConverter* charset_converter,
                     CanonOutput* output,
                     Parsed* output_parsed) {
-  // Reserve enough room in the output for the input, plus some extra so that
-  // we have room if we have to escape a few things without reallocating.
-  output->ReserveSizeIfNeeded(spec_len + 8);
+  output->ReserveSizeIfNeeded(spec_len);
 
   // Remove any whitespace from the middle of the relative URL if necessary.
   // Possibly this will result in copying to the new buffer.
   RawCanonOutputT<CHAR> whitespace_buffer;
   if (whitespace_policy == REMOVE_WHITESPACE)
     spec = RemoveURLWhitespace(spec, spec_len, &whitespace_buffer, &spec_len);
 
   Parsed parsed_input;
 #ifdef WIN32
   // For Windows, we allow things that look like absolute Windows paths to be
@@ skipping 199 matching lines @@
     replacements_no_scheme.SetScheme(NULL, Component());
     return DoReplaceComponents(recanonicalized.data(), recanonicalized.length(),
                                recanonicalized_parsed, replacements_no_scheme,
                                charset_converter, output, out_parsed);
   }
 
   // TODO(csharrison): We could be smarter about size to reserve if this is done
   // in callers below, and the code checks to see which components are being
   // replaced, and with what length. If this ends up being a hot spot it should
   // be changed.
-  output->ReserveSizeIfNeeded(spec_len + 8);
+  output->ReserveSizeIfNeeded(spec_len);
 
   // If we get here, then we know the scheme doesn't need to be replaced, so can
   // just key off the scheme in the spec to know how to do the replacements.
   if (DoCompareSchemeComponent(spec, parsed.scheme, url::kFileScheme)) {
     return ReplaceFileURL(spec, parsed, replacements, charset_converter, output,
                           out_parsed);
   }
   if (DoCompareSchemeComponent(spec, parsed.scheme, url::kFileSystemScheme)) {
     return ReplaceFileSystemURL(spec, parsed, replacements, charset_converter,
                                 output, out_parsed);
@@ skipping 365 matching lines @@
   return DoCompareSchemeComponent(spec, component, compare_to);
 }
 
 bool CompareSchemeComponent(const base::char16* spec,
                             const Component& component,
                             const char* compare_to) {
   return DoCompareSchemeComponent(spec, component, compare_to);
 }
 
 }  // namespace url