Use base::StartWith() in more places when appropriate.

chrome/browser/android/contextualsearch/contextual_search_delegate.cc

 // Copyright 2015 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/android/contextualsearch/contextual_search_delegate.h"
 
 #include <algorithm>
 
 #include "base/base64.h"
 #include "base/command_line.h"
@@ skipping 409 matching lines @@
 // the value of the given parameters.
 void ContextualSearchDelegate::DecodeSearchTermFromJsonResponse(
     const std::string& response,
     std::string* search_term,
     std::string* display_text,
     std::string* alternate_term,
     std::string* prevent_preload,
     int* mention_start,
     int* mention_end,
     std::string* lang) {
-  bool contains_xssi_escape = response.find(kXssiEscape) == 0;
+  bool contains_xssi_escape =
+      base::StartsWith(response, kXssiEscape, base::CompareCase::SENSITIVE);
   const std::string& proper_json =
       contains_xssi_escape ? response.substr(strlen(kXssiEscape)) : response;
   JSONStringValueDeserializer deserializer(proper_json);
   std::unique_ptr<base::Value> root = deserializer.Deserialize(NULL, NULL);
 
   if (root.get() != NULL && root->IsType(base::Value::TYPE_DICTIONARY)) {
     base::DictionaryValue* dict =
         static_cast<base::DictionaryValue*>(root.get());
     dict->GetString(kContextualSearchPreventPreload, prevent_preload);
     dict->GetString(kContextualSearchResponseSearchTermParam, search_term);
@@ skipping 60 matching lines @@
     end_offset -= trim;
   }
   if (result_text.length() > end_offset + padding_each_side_pinned) {
     // Trim the end.
     result_text = result_text.substr(0, end_offset + padding_each_side_pinned);
   }
   *start = start_offset;
   *end = end_offset;
   return result_text;
 }