Safebrowsing: grab lookup_lock_ when clearing browse_gethash_cache_ during update.

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 07f674c9e2289593260ebd4b7312857ece1323de..9e0090e6fb8f568e0705b8d53a3241dd3a097e1f 100644
--- a/chrome/browser/safe_browsing/safe_browsing_database.cc
+++ b/chrome/browser/safe_browsing/safe_browsing_database.cc
@@ -1013,9 +1013,12 @@ bool SafeBrowsingDatabaseNew::UpdateStarted(
     return false;
   }
 
-  // Cached fullhash results must be cleared on every database update (whether
-  // successful or not.)
-  browse_gethash_cache_.clear();
+  {
+    base::AutoLock locked(lookup_lock_);
+    // Cached fullhash results must be cleared on every database update (whether
+    // successful or not.)
+    browse_gethash_cache_.clear();
+  }
 
   UpdateChunkRangesForLists(browse_store_.get(),
                             safe_browsing_util::kMalwareList,