Add parser support for generators.

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index c2305d7bbfeb0bfcd4374651856da0109ce28bd4..570b2bffa4ff07f544b40a4306df2cea91c33cbf 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -4122,6 +4122,10 @@ void HOptimizedGraphBuilder::VisitExpressions(
 
 
 bool HOptimizedGraphBuilder::BuildGraph() {
+  if (info()->function()->is_generator()) {
+    Bailout("function is a generator");
+    return false;
+  }
   Scope* scope = info()->scope();
   if (scope->HasIllegalRedeclaration()) {
     Bailout("function with illegal redeclaration");
@@ -5125,6 +5129,12 @@ void HOptimizedGraphBuilder::VisitReturnStatement(ReturnStatement* stmt) {
 }
 
 
+void HOptimizedGraphBuilder::VisitYield(Yield* expr) {
+  // Generators are not optimized, so we should never get here.
+  UNREACHABLE();
+}
+
+
 void HOptimizedGraphBuilder::VisitWithStatement(WithStatement* stmt) {
   ASSERT(!HasStackOverflow());
   ASSERT(current_block() != NULL);