Reserve space before building potentially large vectors in safe-browsing.

chrome/browser/safe_browsing/safe_browsing_database.cc

Index: chrome/browser/safe_browsing/safe_browsing_database.cc
diff --git a/chrome/browser/safe_browsing/safe_browsing_database.cc b/chrome/browser/safe_browsing/safe_browsing_database.cc
index d3276d476ace8c41abe7a115813ba5c7984d3860..1b49ee08e6ae63d1d7c2ff3e3a96c56c51854e26 100644
--- a/chrome/browser/safe_browsing/safe_browsing_database.cc
+++ b/chrome/browser/safe_browsing/safe_browsing_database.cc
@@ -269,6 +269,7 @@ safe_browsing::PrefixSet* PrefixSetFromAddPrefixes(
   // |prefixes|.  For now, |prefixes| is useful while debugging
   // things.
   std::vector<SBPrefix> prefixes;
+  prefixes.reserve(add_prefixes.size());
   for (size_t i = 0; i < add_prefixes.size(); ++i) {
     prefixes.push_back(add_prefixes[i].prefix);
   }
@@ -1406,6 +1407,7 @@ void SafeBrowsingDatabaseNew::LoadWhitelist(
   }
 
   std::vector<SBFullHash> new_whitelist;
+  new_whitelist.reserve(full_hashes.size());
   for (std::vector<SBAddFullHash>::const_iterator it = full_hashes.begin();
        it != full_hashes.end(); ++it) {
     new_whitelist.push_back(it->full_hash);