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

url/url_canon.h

 // 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.
 
 #ifndef URL_URL_CANON_H_
 #define URL_URL_CANON_H_
 
 #include <stdlib.h>
 #include <string.h>
 
@@ skipping 100 matching lines @@
     if (cur_len_ + str_len > buffer_len_) {
       if (!Grow(cur_len_ + str_len - buffer_len_))
         return;
     }
     for (int i = 0; i < str_len; i++)
       buffer_[cur_len_ + i] = str[i];
     cur_len_ += str_len;
   }
 
   void ReserveSizeIfNeeded(int estimated_size) {
+    // Reserve a bit extra to account for escaped chars.
     if (estimated_size > buffer_len_)
-      Resize(estimated_size);
+      Resize(estimated_size + 8);
   }
 
  protected:
   // Grows the given buffer so that it can fit at least |min_additional|
   // characters. Returns true if the buffer could be resized, false on OOM.
   bool Grow(int min_additional) {
     static const int kMinBufferLen = 16;
     int new_len = (buffer_len_ == 0) ? kMinBufferLen : buffer_len_;
     do {
       if (new_len >= (1 << 30))  // Prevent overflow below.
@@ skipping 782 matching lines @@
                                    bool base_is_file,
                                    const base::char16* relative_url,
                                    const Component& relative_component,
                                    CharsetConverter* query_converter,
                                    CanonOutput* output,
                                    Parsed* out_parsed);
 
 }  // namespace url
 
 #endif  // URL_URL_CANON_H_