Fixes a couple problems with GC 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 30598)
+++ runtime/vm/flow_graph_compiler_x64.cc	(working copy)
@@ -62,10 +62,10 @@
   builder->MarkFrameStart();
 
   // Current PP, FP, and PC.
-  builder->AddPp(current->function(), slot_ix++);
-  builder->AddPcMarker(Function::Handle(), slot_ix++);
+  builder->AddPp(current->code(), slot_ix++);
+  builder->AddPcMarker(Code::Handle(), slot_ix++);
   builder->AddCallerFp(slot_ix++);
-  builder->AddReturnAddress(current->function(), deopt_id(), slot_ix++);
+  builder->AddReturnAddress(current->code(), 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
@@ -83,13 +83,13 @@
   current = current->outer();
   while (current != NULL) {
     // PP, FP, and PC.
-    builder->AddPp(current->function(), slot_ix++);
-    builder->AddPcMarker(previous->function(), slot_ix++);
+    builder->AddPp(current->code(), slot_ix++);
+    builder->AddPcMarker(previous->code(), 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->function(),
+    builder->AddReturnAddress(current->code(),
                               Isolate::ToDeoptAfter(current->deopt_id()),
                               slot_ix++);
 
@@ -120,7 +120,7 @@
   // For the outermost environment, set caller PC, caller PP, and caller FP.
   builder->AddCallerPp(slot_ix++);
   // PC marker.
-  builder->AddPcMarker(previous->function(), slot_ix++);
+  builder->AddPcMarker(previous->code(), slot_ix++);
   builder->AddCallerFp(slot_ix++);
   builder->AddCallerPc(slot_ix++);
 
@@ -1441,6 +1441,10 @@
     __ cmpq(RBX, raw_null);
     __ j(NOT_EQUAL, &is_compiled, Assembler::kNearJump);
     __ call(&StubCode::CompileFunctionRuntimeCallLabel());
+    AddCurrentDescriptor(PcDescriptors::kRuntimeCall,
+                         Isolate::kNoDeoptId,
+                         token_pos);
+    RecordSafepoint(locs);
     __ movq(RBX, FieldAddress(RAX, Function::code_offset()));
     __ Bind(&is_compiled);
   }