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;
+
   // 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