VM: Add infrastructure to support deferred generation of unoptimized code.

runtime/vm/deopt_instructions.h

Index: runtime/vm/deopt_instructions.h
===================================================================
--- runtime/vm/deopt_instructions.h	(revision 44707)
+++ runtime/vm/deopt_instructions.h	(working copy)
@@ -85,6 +85,7 @@
     dest_frame_ = dest_frame;
   }
 
+  Thread* thread() const { return thread_; }
   Zone* zone() const { return thread_->zone(); }
 
   intptr_t source_frame_size() const { return source_frame_size_; }
@@ -153,6 +154,27 @@
         deferred_slots_);
   }
 
+  void DeferRetAddrMaterialization(intptr_t index,
+                                   intptr_t deopt_id,
+                                   intptr_t* slot) {
+    deferred_slots_ = new DeferredRetAddr(
+        index,
+        deopt_id,
+        reinterpret_cast<RawObject**>(slot),
+        deferred_slots_);
+  }
+
+  void DeferPcMarkerMaterialization(intptr_t index, intptr_t* slot) {
+    deferred_slots_ = new DeferredPcMarker(
+        index,
+        reinterpret_cast<RawObject**>(slot),
+        deferred_slots_);
+  }
+
+  void DeferPpMaterialization(intptr_t index, RawObject** slot) {
+    deferred_slots_ = new DeferredPp(index, slot, deferred_slots_);
+  }
+
   DeferredObject* GetDeferredObject(intptr_t idx) const {
     return deferred_objects_[idx];
   }
@@ -409,14 +431,14 @@
   const GrowableObjectArray& object_table() { return object_table_; }
 
   // Return address before instruction.
-  void AddReturnAddress(const Code& code,
+  void AddReturnAddress(const Function& function,
                         intptr_t deopt_id,
                         intptr_t dest_index);
 
   // Copy from optimized frame to unoptimized.
   void AddCopy(Value* value, const Location& source_loc, intptr_t dest_index);
-  void AddPcMarker(const Code& code, intptr_t dest_index);
-  void AddPp(const Code& code, intptr_t dest_index);
+  void AddPcMarker(const Function& function, intptr_t dest_index);
+  void AddPp(const Function& function, intptr_t dest_index);
   void AddCallerFp(intptr_t dest_index);
   void AddCallerPp(intptr_t dest_index);
   void AddCallerPc(intptr_t dest_index);