Implement in-memory byte hints in SimpleCache

net/disk_cache/simple/simple_index_file.h

Index: net/disk_cache/simple/simple_index_file.h
diff --git a/net/disk_cache/simple/simple_index_file.h b/net/disk_cache/simple/simple_index_file.h
index 0f10094b0a4f2a13079ecf083bcd1192b884e47e..b25d00bca72584850612096dd2444cb8d691ad9e 100644
--- a/net/disk_cache/simple/simple_index_file.h
+++ b/net/disk_cache/simple/simple_index_file.h
@@ -67,12 +67,15 @@ class NET_EXPORT_PRIVATE SimpleIndexFile {
 
     SimpleIndex::IndexWriteToDiskReason reason() const { return reason_; }
     uint64_t entry_count() const { return entry_count_; }
+    bool has_memory_entry_data() const { return version_ >= 8; }
 
    private:
     FRIEND_TEST_ALL_PREFIXES(IndexMetadataTest, Basics);
     FRIEND_TEST_ALL_PREFIXES(IndexMetadataTest, Serialize);
     FRIEND_TEST_ALL_PREFIXES(IndexMetadataTest, ReadV6Format);
+    FRIEND_TEST_ALL_PREFIXES(SimpleIndexFileTest, ReadV7Format);
     friend class V6IndexMetadataForTest;
+    friend class V7IndexMetadataForTest;
 
     uint64_t magic_number_;
     uint32_t version_;