Track SimpleCache memory usage in net/ MemoryDumpProvider

net/disk_cache/blockfile/backend_impl.cc

Index: net/disk_cache/blockfile/backend_impl.cc
diff --git a/net/disk_cache/blockfile/backend_impl.cc b/net/disk_cache/blockfile/backend_impl.cc
index f0cdb0c9048fbd964cd11769fcc0ce6514a1418a..7d4f296199bfce07ec22a5e89cd19592fab2eb71 100644
--- a/net/disk_cache/blockfile/backend_impl.cc
+++ b/net/disk_cache/blockfile/backend_impl.cc
@@ -1333,6 +1333,11 @@ void BackendImpl::OnExternalCacheHit(const std::string& key) {
   background_queue_.OnExternalCacheHit(key);
 }
 
+size_t BackendImpl::EstimateMemoryUsage() const {
+  // TODO(xunjieli): Implement this. crbug.com/669108.
+  return 0;
+}
+
 // ------------------------------------------------------------------------
 
 // We just created a new file so we're going to write the header and set the