PVer4: Keep track of the smallest hashes not their sizes. Replace counters with iterators.

components/safe_browsing_db/v4_store.h

Index: components/safe_browsing_db/v4_store.h
diff --git a/components/safe_browsing_db/v4_store.h b/components/safe_browsing_db/v4_store.h
index b88d0f0f18104372b049c45e621bdac436d44c9a..cd71579110fc6eb406feb4a42034bd943ca3cbca 100644
--- a/components/safe_browsing_db/v4_store.h
+++ b/components/safe_browsing_db/v4_store.h
@@ -32,10 +32,11 @@ typedef std::string HashPrefixes;
 // For instance: {4: ["abcd", "bcde", "cdef", "gggg"], 5: ["fffff"]}
 typedef base::hash_map<PrefixSize, HashPrefixes> HashPrefixMap;
 
-// Stores the index of the last element merged from the HashPrefixMap for a
-// given prefix size. For instance: {4:3, 5:1} means that we have already merged
+// Stores the iterator to the last element merged from the HashPrefixMap for a
+// given prefix size.
+// For instance: {4:iter(3), 5:iter(1)} means that we have already merged
 // 3 hash prefixes of length 4, and 1 hash prefix of length 5.
-typedef base::hash_map<PrefixSize, size_t> CounterMap;
+typedef base::hash_map<PrefixSize, HashPrefixes::const_iterator> IteratorMap;
 
 // Enumerate different failure events while parsing the file read from disk for
 // histogramming purposes.  DO NOT CHANGE THE ORDERING OF THESE VALUES.
@@ -209,24 +210,24 @@ class V4Store {
                                              HashPrefixMap* additions_map);
 
   // Get the size of the next unmerged hash prefix in dictionary order from
-  // |hash_prefix_map|. |counter_map| is used to determine which hash prefixes
+  // |hash_prefix_map|. |iterator_map| is used to determine which hash prefixes
   // have been merged already. Returns true if there are any unmerged hash
   // prefixes in the list.
   static bool GetNextSmallestPrefixSize(const HashPrefixMap& hash_prefix_map,
-                                        const CounterMap& counter_map,
+                                        const IteratorMap& iterator_map,
                                         PrefixSize* smallest_prefix_size);
 
   // Returns the next hash prefix of length |prefix_size| from |hash_prefix_map|
-  // that hasn't been merged already. |counter_map| is used to determine the
+  // that hasn't been merged already. |iterator_map| is used to determine the
   // index of the next prefix of size |prefix_size| to merge.
   static HashPrefix GetNextUnmergedPrefixForSize(
       PrefixSize prefix_size,
       const HashPrefixMap& hash_prefix_map,
-      const CounterMap& counter_map);
+      const IteratorMap& iterator_map);
 
-  // Sets a value of 0 in |counter_map| for all keys in |hash_prefix_map|.
-  static void InitializeCounterMap(const HashPrefixMap& hash_prefix_map,
-                                   CounterMap* counter_map);
+  // Sets a value of 0 in |iterator_map| for all keys in |hash_prefix_map|.
+  static void InitializeIteratorMap(const HashPrefixMap& hash_prefix_map,
+                                    IteratorMap* iterator_map);
 
   // Reserve the appropriate string size so that the string size of the merged
   // list is exact. This ignores the space that would otherwise be released by