Introduce a lazy-compile stub for functions.

runtime/vm/raw_object.cc

Index: runtime/vm/raw_object.cc
===================================================================
--- runtime/vm/raw_object.cc	(revision 34118)
+++ runtime/vm/raw_object.cc	(working copy)
@@ -137,7 +137,7 @@
       case kPcDescriptorsCid: {
         const RawPcDescriptors* raw_descriptors =
             reinterpret_cast<const RawPcDescriptors*>(this);
-        intptr_t num_descriptors = Smi::Value(raw_descriptors->ptr()->length_);
+        intptr_t num_descriptors = raw_descriptors->ptr()->length_;
         instance_size = PcDescriptors::InstanceSize(num_descriptors);
         break;
       }
@@ -495,19 +495,13 @@
 
 intptr_t RawPcDescriptors::VisitPcDescriptorsPointers(
     RawPcDescriptors* raw_obj, ObjectPointerVisitor* visitor) {
-  RawPcDescriptors* obj = raw_obj->ptr();
-  intptr_t length = Smi::Value(obj->length_);
-  visitor->VisitPointer(reinterpret_cast<RawObject**>(&obj->length_));
-  return PcDescriptors::InstanceSize(length);
+  return PcDescriptors::InstanceSize(raw_obj->ptr()->length_);
 }
 
 
 intptr_t RawStackmap::VisitStackmapPointers(RawStackmap* raw_obj,
                                             ObjectPointerVisitor* visitor) {
-  RawStackmap* obj = raw_obj->ptr();
-  intptr_t length = obj->length_;
-  visitor->VisitPointer(reinterpret_cast<RawObject**>(&obj->code_));
-  return Stackmap::InstanceSize(length);
+  return Stackmap::InstanceSize(raw_obj->ptr()->length_);
 }