Disk cache: Add a hash to the entry's internal data.

net/data/cache_tests/dirty_entry2/contents.txt

Index: net/data/cache_tests/dirty_entry2/contents.txt
===================================================================
--- net/data/cache_tests/dirty_entry2/contents.txt	(revision 110637)
+++ net/data/cache_tests/dirty_entry2/contents.txt	(working copy)
@@ -1,67 +0,0 @@
-Index header:
-num_entries: 2
-num_bytes: 27
-this_id: 1
-table_len: 64k
-
-head: 0x90000001
-tail: 0x90000000
-
-Address: 0xa0010002
-Address: 0xa0010003
-
--------------------------------
-
-entry:
-Address: 0xa0010002
-hash: 0x687d1422
-next: 0
-rankings_node: 0x90000000
-key_len: 13
-long_key: 0
-data_size: 0's
-data_addr: 0's
-key: "the first key"
-
-rankings:
-Address: 0x90000000
-next: 0x90000000
-prev: 0x90000001
-contents: 0xa0010002
-dirty: 0
-pointer: 0
-
--------------------------------
-
-entry:
-Address: 0xa0010003
-hash: 0x63909ecb
-next: 0
-rankings_node: 0x90000001
-key_len: 14
-long_key: 0
-data_size: 0's
-data_addr: 0's
-key: "some other key"
-
-rankings:
-Address: 0x90000001
-next: 0x90000000
-prev: 0x90000001
-contents: 0xa0010003
-dirty: 2                  <- Next id!.
-pointer: 0x0169dc48       <- Invalid.
-
-================================
-
-Generated with:
-
-disk_cache::Entry *entry;
-ASSERT_TRUE(cache_->CreateEntry("the first key", &entry));
-entry->Close();
-
-ASSERT_TRUE(cache_->CreateEntry("some other key", &entry));
-entry->Close();                                              <---- Edit value*
-
-* Edit the value with the debugger before it is saved to disk (break on
-the destructor of EntryImpl and skip the line that clears "pointer")