[AiS] Make base64 encoding URL-safe.

chrome/browser/autocomplete/search_provider.cc

 // Copyright 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 "chrome/browser/autocomplete/search_provider.h"
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/base64.h"
@@ skipping 1134 matching lines @@
 }
 
 std::string SearchProvider::GetSessionToken() {
   base::TimeTicks current_time(base::TimeTicks::Now());
   // Renew token if it expired.
   if (current_time > token_expiration_time_) {
     const size_t kTokenBytes = 12;
     std::string raw_data;
     base::RandBytes(WriteInto(&raw_data, kTokenBytes + 1), kTokenBytes);
     base::Base64Encode(raw_data, &current_token_);
+
+    // Make the base64 encoded value URL and filename safe(see RFC 3548).
+    std::replace(current_token_.begin(), current_token_.end(), '+', '-');
+    std::replace(current_token_.begin(), current_token_.end(), '/', '_');
   }
 
   // Extend expiration time another 60 seconds.
   token_expiration_time_ = current_time + base::TimeDelta::FromSeconds(60);
 
   return current_token_;
 }