New hydrogen instruction to reduce cost of growing an array on keyed stores.

src/runtime/runtime.h

Index: src/runtime/runtime.h
diff --git a/src/runtime/runtime.h b/src/runtime/runtime.h
index 0f5624784a4cefee720d6bf06b04c5922ba8c170..8eeffdf053a1c1bb921f559f8980793470202851 100644
--- a/src/runtime/runtime.h
+++ b/src/runtime/runtime.h
@@ -43,7 +43,7 @@ namespace internal {
   F(ArrayConstructorWithSubclassing, -1, 1)                           \
   F(InternalArrayConstructor, -1, 1)                                  \
   F(NormalizeElements, 1, 1)                                          \
-  F(GrowArrayElements, 3, 1)                                          \
+  F(GrowArrayElements, 2, 1)                                          \
   F(HasComplexElements, 1, 1)                                         \
   F(ForInCacheArrayLength, 2, 1) /* TODO(turbofan): Only temporary */ \
   F(IsArray, 1, 1)                                                    \