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

src/code-stubs.cc

Index: src/code-stubs.cc
diff --git a/src/code-stubs.cc b/src/code-stubs.cc
index 8a3728366d9e9a73e3ae2f140f50c06a928f61e7..d01d38727c6a803445ad46f959c8d883b8d0b492 100644
--- a/src/code-stubs.cc
+++ b/src/code-stubs.cc
@@ -744,6 +744,12 @@ void AllocateHeapNumberStub::InitializeDescriptor(
 }
 
 
+void AllocateMutableHeapNumberStub::InitializeDescriptor(
+    CodeStubDescriptor* descriptor) {
+  descriptor->Initialize();
+}
+
+
 void AllocateInNewSpaceStub::InitializeDescriptor(
     CodeStubDescriptor* descriptor) {
   descriptor->Initialize();