Refactor cache counting into a separate helper class

net/http/mock_http_cache.cc

Index: net/http/mock_http_cache.cc
diff --git a/net/http/mock_http_cache.cc b/net/http/mock_http_cache.cc
index 9fc8ced93ce4c502f56f42508b8abc454208cd9b..c7f18bf09cf348511f4349a3b3d120d566664f15 100644
--- a/net/http/mock_http_cache.cc
+++ b/net/http/mock_http_cache.cc
@@ -103,6 +103,14 @@ int32_t MockDiskEntry::GetDataSize(int index) const {
   return static_cast<int32_t>(data_[index].size());
 }
 
+int64_t MockDiskEntry::GetEntrySize() const {
+  int64_t size = key_.size();
+  for (int i = 0; i < kNumCacheEntryDataIndices; ++i) {
+    size += GetDataSize(i);
+  }
+  return size;
+}
+
 int MockDiskEntry::ReadData(int index,
                             int offset,
                             IOBuffer* buf,