Add a size estimation mechanism to StoragePartitionHttpCacheDataRemover.

net/http/mock_http_cache.h

Index: net/http/mock_http_cache.h
diff --git a/net/http/mock_http_cache.h b/net/http/mock_http_cache.h
index 632bb3e63c16996290e5ed945c6d7f7909eea5c0..554b815c73911105d381a472996414cacd8c31d7 100644
--- a/net/http/mock_http_cache.h
+++ b/net/http/mock_http_cache.h
@@ -127,6 +127,7 @@ class MockDiskCache : public disk_cache::Backend {
                          const CompletionCallback& callback) override;
   int DoomEntriesSince(base::Time initial_time,
                        const CompletionCallback& callback) override;
+  int CalculateSizeOfAllEntries(const CompletionCallback& callback) override;
   scoped_ptr<Iterator> CreateIterator() override;
   void GetStats(base::StringPairs* stats) override;
   void OnExternalCacheHit(const std::string& key) override;