Reland: Fix bug in field type tracking and polymorphic inlining.

runtime/vm/flow_graph_builder.h

Index: runtime/vm/flow_graph_builder.h
===================================================================
--- runtime/vm/flow_graph_builder.h	(revision 27690)
+++ runtime/vm/flow_graph_builder.h	(working copy)
@@ -98,13 +98,14 @@
 
 
 // Build a flow graph from a parsed function's AST.
-class FlowGraphBuilder: public ValueObject {
+class FlowGraphBuilder: public ZoneAllocated {
  public:
   // The inlining context is NULL if not inlining.  The osr_id is the deopt
   // id of the OSR entry or Isolate::kNoDeoptId if not compiling for OSR.
   FlowGraphBuilder(ParsedFunction* parsed_function,
                    const Array& ic_data_array,
                    InlineExitCollector* exit_collector,
+                   GrowableArray<const Field*>* guarded_fields,
                    intptr_t osr_id);
 
   FlowGraph* BuildGraph();
@@ -147,6 +148,12 @@
   bool IsInlining() const { return (exit_collector_ != NULL); }
   InlineExitCollector* exit_collector() const { return exit_collector_; }
 
+  GrowableArray<const Field*>* guarded_fields() const {
+    return guarded_fields_;
+  }
+
+  void AddToGuardedFields(const Field& field) const;
+
   intptr_t args_pushed() const { return args_pushed_; }
   void add_args_pushed(intptr_t n) { args_pushed_ += n; }
 
@@ -169,6 +176,7 @@
   const intptr_t num_non_copied_params_;
   const intptr_t num_stack_locals_;  // Does not include any parameters.
   InlineExitCollector* const exit_collector_;
+  GrowableArray<const Field*>* guarded_fields_;
 
   intptr_t last_used_block_id_;
   intptr_t context_level_;