[turbofan] Add support for transitioning stores to double fields.

src/code-stubs.h

Index: src/code-stubs.h
diff --git a/src/code-stubs.h b/src/code-stubs.h
index fb46723ff1e40b5f84570bb4ed36047ad5bfe3b6..959881262603c221c3e4540d505a68f0fa858330 100644
--- a/src/code-stubs.h
+++ b/src/code-stubs.h
@@ -61,6 +61,7 @@ namespace internal {
   V(VectorKeyedStoreIC)                     \
   /* HydrogenCodeStubs */                   \
   V(AllocateHeapNumber)                     \
+  V(AllocateMutableHeapNumber)              \
   V(AllocateInNewSpace)                     \
   V(ArrayNArgumentsConstructor)             \
   V(ArrayNoArgumentConstructor)             \
@@ -2658,6 +2659,17 @@ class AllocateHeapNumberStub final : public HydrogenCodeStub {
 };
 
 
+class AllocateMutableHeapNumberStub final : public HydrogenCodeStub {
+ public:
+  explicit AllocateMutableHeapNumberStub(Isolate* isolate)
+      : HydrogenCodeStub(isolate) {}
+
+ private:
+  DEFINE_CALL_INTERFACE_DESCRIPTOR(AllocateMutableHeapNumber);
+  DEFINE_HYDROGEN_CODE_STUB(AllocateMutableHeapNumber, HydrogenCodeStub);
+};
+
+
 class AllocateInNewSpaceStub final : public HydrogenCodeStub {
  public:
   explicit AllocateInNewSpaceStub(Isolate* isolate)