Proof of concept: API for doing only one parsing pass instead of first preparsing and then parsing.

src/parser.h

Index: src/parser.h
diff --git a/src/parser.h b/src/parser.h
index 799ec5860d55bbc89f69d0b61c0bfc4990a2fe52..af69f889a3cba4fefe091bfdbe6a73bf5ba780e7 100644
--- a/src/parser.h
+++ b/src/parser.h
@@ -609,14 +609,14 @@ class Parser : public ParserBase<ParserTraits> {
   // Report syntax error
   void ReportInvalidPreparseData(Handle<String> name, bool* ok);
 
-  void set_pre_parse_data(ScriptDataImpl *data) {
-    pre_parse_data_ = data;
-    symbol_cache_.Initialize(data ? data->symbol_count() : 0, zone());
+  void set_cached_data(ScriptDataImpl** data) {
+    cached_data_ = data;
+    symbol_cache_.Initialize(data && *data ? (*data)->symbol_count() : 0,
+                             zone());
   }
 
   bool inside_with() const { return scope_->inside_with(); }
   Mode mode() const { return mode_; }
-  ScriptDataImpl* pre_parse_data() const { return pre_parse_data_; }
   Scope* DeclarationScope(VariableMode mode) {
     return IsLexicalVariableMode(mode)
         ? scope_ : scope_->DeclarationScope();
@@ -788,6 +788,7 @@ class Parser : public ParserBase<ParserTraits> {
   Scope* original_scope_;  // for ES5 function declarations in sloppy eval
   Target* target_stack_;  // for break, continue statements
   ScriptDataImpl* pre_parse_data_;
+  ScriptDataImpl** cached_data_;
 
   Mode mode_;