Tighten up assertions checking GC-safety of stub calls.

src/x64/code-stubs-x64.h

Index: src/x64/code-stubs-x64.h
diff --git a/src/x64/code-stubs-x64.h b/src/x64/code-stubs-x64.h
index e3be69e5072754b08e9c925fe391b1e31ac74d17..698ba403cda6d5b7db64d0d0b039c7decdfd537d 100644
--- a/src/x64/code-stubs-x64.h
+++ b/src/x64/code-stubs-x64.h
@@ -66,7 +66,7 @@ class StoreBufferOverflowStub: public CodeStub {
 
   void Generate(MacroAssembler* masm);
 
-  virtual bool CompilingCallsToThisStubIsGCSafe() { return true; }
+  virtual bool IsPregenerated() { return true; }
   static void GenerateFixedRegStubsAheadOfTime();
   virtual bool SometimesSetsUpAFrame() { return false; }
 
@@ -497,7 +497,7 @@ class RecordWriteStub: public CodeStub {
     INCREMENTAL_COMPACTION
   };
 
-  virtual bool CompilingCallsToThisStubIsGCSafe();
+  virtual bool IsPregenerated();
   static void GenerateFixedRegStubsAheadOfTime();
   virtual bool SometimesSetsUpAFrame() { return false; }