Merge flush code phase into marking phase.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index a838bd5be843010e7276eae6c577f3f884b2d7f9..5d4aebcd8029dbfba98c8866bb9c9bc9a43ebc10 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -3371,6 +3371,8 @@ class SharedFunctionInfo: public HeapObject {
   // [construct stub]: Code stub for constructing instances of this function.
   DECL_ACCESSORS(construct_stub, Code)
 
+  inline Code* unchecked_code();
+
   // Returns if this function has been compiled to native code yet.
   inline bool is_compiled();
 
@@ -3478,6 +3480,15 @@ class SharedFunctionInfo: public HeapObject {
   inline bool allows_lazy_compilation();
   inline void set_allows_lazy_compilation(bool flag);
 
+  // Indicates how many full GCs this function has survived with assigned
+  // code object. Used to determine when it is relatively safe to flush
+  // this code object and replace it with lazy compilation stub.
+  // Age is reset when GC notices that the code object is referenced
+  // from the stack or compilation cache.
+  inline int code_age();
+  inline void set_code_age(int age);
+
+
   // Check whether a inlined constructor can be generated with the given
   // prototype.
   bool CanGenerateInlineConstructor(Object* prototype);
@@ -3608,6 +3619,8 @@ class SharedFunctionInfo: public HeapObject {
   static const int kHasOnlySimpleThisPropertyAssignments = 0;
   static const int kTryFullCodegen = 1;
   static const int kAllowLazyCompilation = 2;
+  static const int kCodeAgeShift = 3;
+  static const int kCodeAgeMask = 7;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(SharedFunctionInfo);
 };
@@ -3623,6 +3636,8 @@ class JSFunction: public JSObject {
   // can be shared by instances.
   DECL_ACCESSORS(shared, SharedFunctionInfo)
 
+  inline SharedFunctionInfo* unchecked_shared();
+
   // [context]: The context for this function.
   inline Context* context();
   inline Object* unchecked_context();
@@ -3635,6 +3650,8 @@ class JSFunction: public JSObject {
   inline Code* code();
   inline void set_code(Code* value);
 
+  inline Code* unchecked_code();
+
   // Tells whether this function is builtin.
   inline bool IsBuiltin();