Allow empty UKM entries to be recorded.

components/ukm/ukm_entry_builder.cc

Index: components/ukm/ukm_entry_builder.cc
diff --git a/components/ukm/ukm_entry_builder.cc b/components/ukm/ukm_entry_builder.cc
index fd640342ba5d4124319121d70e9432cf0ad1911f..fdff949038c67908bcae8bd96b215a0bc48ceb61 100644
--- a/components/ukm/ukm_entry_builder.cc
+++ b/components/ukm/ukm_entry_builder.cc
@@ -17,9 +17,6 @@ UkmEntryBuilder::UkmEntryBuilder(const UkmService::AddEntryCallback& callback,
       entry_(new UkmEntry(source_id, event_name)) {}
 
 UkmEntryBuilder::~UkmEntryBuilder() {
-  if (entry_->metrics_.empty())
-    return;
-
   add_entry_callback_.Run(std::move(entry_));
 }