Add a size estimation mechanism to StoragePartitionHttpCacheDataRemover.

net/disk_cache/disk_cache.h

Index: net/disk_cache/disk_cache.h
diff --git a/net/disk_cache/disk_cache.h b/net/disk_cache/disk_cache.h
index 84c1ee99516654258486494a8afeacfb70ddc31d..b7a298a9aa5d5d0601c18826ea2be3c47c7b0b36 100644
--- a/net/disk_cache/disk_cache.h
+++ b/net/disk_cache/disk_cache.h
@@ -145,6 +145,16 @@ class NET_EXPORT Backend {
   virtual int DoomEntriesSince(base::Time initial_time,
                                const CompletionCallback& callback) = 0;
 
+  // Calculate the total size of entries satisfying the condition
+  // |initial_time| <= access_time < |end_time|. The return value is the number
+  // of bytes written or a net error code. If this method returns
+  // ERR_IO_PENDING, the |callback| will be invoked when the operation
+  // completes.
+  virtual int CalculateSizeOfEntriesBetween(
+      base::Time initial_time,
+      base::Time end_time,
+      const CompletionCallback& callback) = 0;
+
   // Returns an iterator which will enumerate all entries of the cache in an
   // undefined order.
   virtual scoped_ptr<Iterator> CreateIterator() = 0;
@@ -183,6 +193,10 @@ class NET_EXPORT Entry {
   // Returns the size of the cache data with the given index.
   virtual int32 GetDataSize(int index) const = 0;
 
+  // Returns the total size of this entry, a sum of the cached data for each
+  // valid index.
+  virtual int GetEntrySize() const = 0;

[pasko, 2015/09/04 14:11:50]

I think it is a _bad_ interface to use for calculating overall size of the
cache.

This suggests that all entries in the cache should be opened one by one to get
the overall size. That can be very inefficient (it *is* inefficient in
simplecache compared to how SimpleIndex would do it).

Can we avoid exposing this and have only new interface in the backend exposed?

If a (deficient) backend can only calculate size by opening everything, it has a
way to talk to EntryImpl/whatever directly.

[msramek, 2015/09/04 16:56:47]

Makes sense. I removed GetEntrySize from everywhere except EntryImpl.

+
   // Copies cached data into the given buffer of length |buf_len|. Returns the
   // number of bytes read or a network error code. If this function returns
   // ERR_IO_PENDING, the completion callback will be called on the current