Lazily save double registers for HCallRuntime instructions within Hydrogen code stubs.

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index d69e613605feba5a9ac863aaf3cefeb319dcaf41..7517b908ca5790b8c5dc76caf6200e193edef8a3 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -973,6 +973,9 @@ void HCallNewArray::PrintDataTo(StringStream* stream) {
 
 void HCallRuntime::PrintDataTo(StringStream* stream) {
   stream->Add("%o ", *name());
+  if (save_doubles() == kSaveFPRegs) {
+    stream->Add("[save doubles] ");
+  }
   stream->Add("#%d", argument_count());
 }