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

runtime/vm/flow_graph_compiler_x64.cc

Index: runtime/vm/flow_graph_compiler_x64.cc
===================================================================
--- runtime/vm/flow_graph_compiler_x64.cc	(revision 44707)
+++ runtime/vm/flow_graph_compiler_x64.cc	(working copy)
@@ -95,10 +95,12 @@
   builder->MarkFrameStart();
 
   // Current PP, FP, and PC.
-  builder->AddPp(current->code(), slot_ix++);
-  builder->AddPcMarker(Code::Handle(), slot_ix++);
+  builder->AddPp(Function::Handle(current->code().function()), slot_ix++);
+  builder->AddPcMarker(Function::Handle(), slot_ix++);
   builder->AddCallerFp(slot_ix++);
-  builder->AddReturnAddress(current->code(), deopt_id(), slot_ix++);
+  builder->AddReturnAddress(Function::Handle(current->code().function()),
+                            deopt_id(),
+                            slot_ix++);
 
   // Emit all values that are needed for materialization as a part of the
   // expression stack for the bottom-most frame. This guarantees that GC
@@ -116,13 +118,14 @@
   current = current->outer();
   while (current != NULL) {
     // PP, FP, and PC.
-    builder->AddPp(current->code(), slot_ix++);
-    builder->AddPcMarker(previous->code(), slot_ix++);
+    builder->AddPp(Function::Handle(current->code().function()), slot_ix++);
+    builder->AddPcMarker(Function::Handle(previous->code().function()),
+                         slot_ix++);
     builder->AddCallerFp(slot_ix++);
 
     // For any outer environment the deopt id is that of the call instruction
     // which is recorded in the outer environment.
-    builder->AddReturnAddress(current->code(),
+    builder->AddReturnAddress(Function::Handle(current->code().function()),
                               Isolate::ToDeoptAfter(current->deopt_id()),
                               slot_ix++);
 
@@ -153,7 +156,8 @@
   // For the outermost environment, set caller PC, caller PP, and caller FP.
   builder->AddCallerPp(slot_ix++);
   // PC marker.
-  builder->AddPcMarker(previous->code(), slot_ix++);
+  builder->AddPcMarker(Function::Handle(previous->code().function()),
+                       slot_ix++);
   builder->AddCallerFp(slot_ix++);
   builder->AddCallerPc(slot_ix++);