Implement in-memory byte hints in SimpleCache

net/disk_cache/simple/simple_version_upgrade.cc

Index: net/disk_cache/simple/simple_version_upgrade.cc
diff --git a/net/disk_cache/simple/simple_version_upgrade.cc b/net/disk_cache/simple/simple_version_upgrade.cc
index 1c4a7ba2b2bd569b593d5da059b96c0a0bce0586..b21dbbd22e7fb030649d706e57e23722c51afbff 100644
--- a/net/disk_cache/simple/simple_version_upgrade.cc
+++ b/net/disk_cache/simple/simple_version_upgrade.cc
@@ -198,6 +198,12 @@ bool UpgradeSimpleCacheOnDisk(const base::FilePath& path,
     // the V7 index reader is backwards compatible.
     version_from++;
   }
+
+  if (version_from == 7) {
+    // Likewise, V7 -> V8 is handled entirely by the index reader.

[pasko, 2017/06/29 16:31:49]

I am curious about this scenario:
1. we read the index as if it is v7
2. we write cache version down to the fake index as v8
3. chrome crashes or gets killed by the OS before the new version of the index
is flushed

On the next start this would make the simple_index_file attempt to read a v7
index as if it is a v8 which would read all the entry sizes incorrectly, right?

[Maks Orlovich, 2017/08/23 19:29:06]

Answered elsewhere.

+    version_from++;
+  }
+
   DCHECK_EQ(kSimpleVersion, version_from);
 
   if (!new_fake_index_needed)