- Make use of the fact that idents and literals are symbols.

runtime/vm/scanner.cc

Index: runtime/vm/scanner.cc
===================================================================
--- runtime/vm/scanner.cc	(revision 36194)
+++ runtime/vm/scanner.cc	(working copy)
@@ -369,9 +369,10 @@
   }
   if (current_token_.kind != Token::kILLEGAL) {
     intptr_t len = lookahead_pos_ - token_start_;
-    current_token_.literal =
-        &String::ZoneHandle(
-            String::SubString(source_, token_start_, len, Heap::kOld));
+    String& str = String::ZoneHandle(
+        String::SubString(source_, token_start_, len, Heap::kOld));
+    str = Symbols::New(str);
+    current_token_.literal = &str;
   }
 }