Make FastNewFunctionContextStub take slots parameter

src/crankshaft/x64/lithium-codegen-x64.cc

Index: src/crankshaft/x64/lithium-codegen-x64.cc
diff --git a/src/crankshaft/x64/lithium-codegen-x64.cc b/src/crankshaft/x64/lithium-codegen-x64.cc
index b0c10add4f3115cad40365ed4e172e95b6d4b21b..f5c28466b2a77f82528ddd85ac08d588a4573df4 100644
--- a/src/crankshaft/x64/lithium-codegen-x64.cc
+++ b/src/crankshaft/x64/lithium-codegen-x64.cc
@@ -181,14 +181,12 @@ void LCodeGen::DoPrologue(LPrologue* instr) {
       __ Push(info()->scope()->GetScopeInfo(info()->isolate()));
       __ CallRuntime(Runtime::kNewScriptContext);
       deopt_mode = Safepoint::kLazyDeopt;
-    } else if (slots <= FastNewFunctionContextStub::kMaximumSlots) {
-      FastNewFunctionContextStub stub(isolate(), slots);
+    } else {
+      FastNewFunctionContextStub stub(isolate());
+      __ Set(FastNewFunctionContextDescriptor::SlotsRegister(), slots);
       __ CallStub(&stub);
       // Result of FastNewFunctionContextStub is always in new space.
       need_write_barrier = false;
-    } else {
-      __ Push(rdi);
-      __ CallRuntime(Runtime::kNewFunctionContext);
     }
     RecordSafepoint(deopt_mode);