Refactor cache counting into a separate helper class

net/disk_cache/backend_unittest.cc

Index: net/disk_cache/backend_unittest.cc
diff --git a/net/disk_cache/backend_unittest.cc b/net/disk_cache/backend_unittest.cc
index e92dd9b2f59ce8d07ee293ce6e536c16402ec1ce..6c0ad6cc7b2c90ed0d250b9568672e26d4c3c888 100644
--- a/net/disk_cache/backend_unittest.cc
+++ b/net/disk_cache/backend_unittest.cc
@@ -1805,6 +1805,9 @@ void DiskCacheBackendTest::BackendCalculateSizeOfAllEntries() {
   // sizes 0, 1, ..., count - 1 bytes.
   std::set<std::string> key_pool;
   CreateSetOfRandomEntries(&key_pool);
+  // Keep track of the sum of the individual entry sizes and check that it is
+  // consistent with CalculateSizeOfAllEntries().
+  int64_t sum_entry_size = 0;
 
   int count = 0;
   for (std::string key : key_pool) {
@@ -1816,6 +1819,7 @@ void DiskCacheBackendTest::BackendCalculateSizeOfAllEntries() {
     disk_cache::Entry* entry;
     ASSERT_THAT(OpenEntry(key, &entry), IsOk());
     ASSERT_EQ(count, WriteData(entry, count % 2, 0, buffer.get(), count, true));
+    sum_entry_size += entry->GetEntrySize();
     entry->Close();
 
     ++count;
@@ -1827,6 +1831,7 @@ void DiskCacheBackendTest::BackendCalculateSizeOfAllEntries() {
   for (std::string key : key_pool)
     total_metadata_size += GetEntryMetadataSize(key);
   EXPECT_EQ((count - 1) * count / 2 + total_metadata_size, result);
+  EXPECT_EQ(sum_entry_size, result);
 
   // Add another entry and test if the size is updated. Then remove it and test
   // if the size is back to original value.
@@ -1840,6 +1845,8 @@ void DiskCacheBackendTest::BackendCalculateSizeOfAllEntries() {
     ASSERT_THAT(CreateEntry(key, &entry), IsOk());
     ASSERT_EQ(last_entry_size,
               WriteData(entry, 0, 0, buffer.get(), last_entry_size, true));
+    ASSERT_EQ(last_entry_size + GetEntryMetadataSize(key),
+              entry->GetEntrySize());
     entry->Close();
 
     int new_result = CalculateSizeOfAllEntries();
@@ -1848,6 +1855,7 @@ void DiskCacheBackendTest::BackendCalculateSizeOfAllEntries() {
     DoomEntry(key);
     new_result = CalculateSizeOfAllEntries();
     EXPECT_EQ(result, new_result);
+    EXPECT_EQ(sum_entry_size, new_result);
   }
 
   // After dooming the entries, the size should be back to zero.