Lookup getter/setter symbols before alllocating them, thus eliminating extra String allocations in …

runtime/vm/symbols.h

Index: runtime/vm/symbols.h
diff --git a/runtime/vm/symbols.h b/runtime/vm/symbols.h
index f5f7bbfda709eff52119495018f90b74604ae1b3..726988dd802a6ebbf1e0cb60acfca692b322a54c 100644
--- a/runtime/vm/symbols.h
+++ b/runtime/vm/symbols.h
@@ -611,6 +611,13 @@ class Symbols : public AllStatic {
 
   static void DumpStats();
 
+  // Returns Symbol::Null if no symbol is found.
+  template<typename StringType>
+  static RawString* Lookup(const StringType& str);
+
+  // Returns Symbol::Null if no symbol is found.
+  static RawString* LookupFromConcat(const String& str1, const String& str2);
+
  private:
   enum {
     kInitialVMIsolateSymtabSize = 1024,