Precompilation: drop unused types and type arguments and empty classes and libraries.

runtime/vm/class_table.cc

Index: runtime/vm/class_table.cc
diff --git a/runtime/vm/class_table.cc b/runtime/vm/class_table.cc
index 3296bcccb7a36c02c06aff57412ff59d54b07cca..7129cf8f0ab3393ac35f09d913277797b0376e2c 100644
--- a/runtime/vm/class_table.cc
+++ b/runtime/vm/class_table.cc
@@ -180,6 +180,13 @@ void ClassTable::RegisterAt(intptr_t index, const Class& cls) {
 }
 
 
+#if defined(DEBUG)
+void ClassTable::Unregister(intptr_t index) {
+  table_[index] = 0;
+}
+#endif
+
+
 void ClassTable::VisitObjectPointers(ObjectPointerVisitor* visitor) {
   ASSERT(visitor != NULL);
   visitor->VisitPointers(reinterpret_cast<RawObject**>(&table_[0]), top_);