Cleanup: Make ExtensionIconSet::Get return a const std::string& rather than a

extensions/common/extension_icon_set.cc

 // Copyright 2014 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 "extensions/common/extension_icon_set.h"
 
 #include "base/logging.h"
+#include "base/strings/string_util.h"
 
 ExtensionIconSet::ExtensionIconSet() {}
 
 ExtensionIconSet::~ExtensionIconSet() {}
 
 void ExtensionIconSet::Clear() {
   map_.clear();
 }
 
 void ExtensionIconSet::Add(int size, const std::string& path) {
   DCHECK(!path.empty() && path[0] != '/');
   map_[size] = path;
 }
 
-std::string ExtensionIconSet::Get(int size, MatchType match_type) const {
+const std::string& ExtensionIconSet::Get(int size, MatchType match_type) const {
   // The searches for MATCH_BIGGER and MATCH_SMALLER below rely on the fact that
   // std::map is sorted. This is per the spec, so it should be safe to rely on.
   if (match_type == MATCH_EXACTLY) {
     IconMap::const_iterator result = map_.find(size);
-    return result == map_.end() ? std::string() : result->second;
+    return result == map_.end() ? base::EmptyString() : result->second;
   } else if (match_type == MATCH_SMALLER) {
     IconMap::const_reverse_iterator result = map_.rend();
     for (IconMap::const_reverse_iterator iter = map_.rbegin();
          iter != map_.rend(); ++iter) {
       if (iter->first <= size) {
         result = iter;
         break;
       }
     }
-    return result == map_.rend() ? std::string() : result->second;
+    return result == map_.rend() ? base::EmptyString() : result->second;
   } else {
     DCHECK(match_type == MATCH_BIGGER);
     IconMap::const_iterator result = map_.end();
     for (IconMap::const_iterator iter = map_.begin(); iter != map_.end();
          ++iter) {
       if (iter->first >= size) {
         result = iter;
         break;
       }
     }
-    return result == map_.end() ? std::string() : result->second;
+    return result == map_.end() ? base::EmptyString() : result->second;
   }
 }
 
 bool ExtensionIconSet::ContainsPath(const std::string& path) const {
   return GetIconSizeFromPath(path) != 0;
 }
 
 int ExtensionIconSet::GetIconSizeFromPath(const std::string& path) const {
   if (path.empty())
     return 0;
 
   DCHECK_NE(path[0], '/') <<
       "ExtensionIconSet stores icon paths without leading slash.";
 
   for (IconMap::const_iterator iter = map_.begin(); iter != map_.end();
        ++iter) {
     if (iter->second == path)
       return iter->first;
   }
 
   return 0;
 }