Make preparsing data reusable.

src/parser.h

Index: src/parser.h
diff --git a/src/parser.h b/src/parser.h
index 8bab92d5a923c0833d4af3bec86c0adede5458b0..8c00857276388d3640e2e217d5c99f18f51f6f2d 100644
--- a/src/parser.h
+++ b/src/parser.h
@@ -101,10 +101,7 @@ class ScriptDataImpl : public ScriptData {
  public:
   explicit ScriptDataImpl(Vector<unsigned> store)
       : store_(store),
-        function_index_(kHeaderSize),
-        owns_store_(true) {
-    Initialize();
-  }
+        owns_store_(true) { }
 
   // Create an empty ScriptDataImpl that is guaranteed to not satisfy
   // a SanityCheck.
@@ -190,10 +187,8 @@ class ScriptDataImpl : public ScriptData {
   ScriptDataImpl(const char* backing_store, int length)
       : store_(reinterpret_cast<unsigned*>(const_cast<char*>(backing_store)),
                length / sizeof(unsigned)),
-        function_index_(kHeaderSize),
         owns_store_(false) {
     ASSERT_EQ(0, reinterpret_cast<intptr_t>(backing_store) % sizeof(unsigned));
-    Initialize();
   }
 
   // Read strings written by ParserRecorder::WriteString.