Parse harmony let declarations.

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 402f22055c64919ad060ec28b333cfad311aa55e..5a5f14dc657385cda8d99072134ebdcd4ef7f588 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -35,6 +35,7 @@
 #include "debug.h"
 #include "deoptimizer.h"
 #include "execution.h"
+#include "flags.h"
 #include "global-handles.h"
 #include "heap-profiler.h"
 #include "messages.h"
@@ -1405,7 +1406,7 @@ void ObjectTemplate::SetInternalFieldCount(int value) {
 ScriptData* ScriptData::PreCompile(const char* input, int length) {
   i::Utf8ToUC16CharacterStream stream(
       reinterpret_cast<const unsigned char*>(input), length);
-  return i::ParserApi::PreParse(&stream, NULL);
+  return i::ParserApi::PreParse(&stream, NULL, i::FLAG_harmony_block_scoping);
 }
 
 
@@ -1414,10 +1415,10 @@ ScriptData* ScriptData::PreCompile(v8::Handle<String> source) {
   if (str->IsExternalTwoByteString()) {
     i::ExternalTwoByteStringUC16CharacterStream stream(
       i::Handle<i::ExternalTwoByteString>::cast(str), 0, str->length());
-    return i::ParserApi::PreParse(&stream, NULL);
+    return i::ParserApi::PreParse(&stream, NULL, i::FLAG_harmony_block_scoping);
   } else {
     i::GenericStringUC16CharacterStream stream(str, 0, str->length());
-    return i::ParserApi::PreParse(&stream, NULL);
+    return i::ParserApi::PreParse(&stream, NULL, i::FLAG_harmony_block_scoping);
   }
 }