Simplify ObjectVisitor for external references.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 299ca2dcacc5be83e8e91c4a43177b7892bfb0b3..ec78d27e8ab50c0df2b00abfe74d89b5325e88d0 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -10340,6 +10340,9 @@ class ObjectVisitor BASE_EMBEDDED {
   // [start, end). Any or all of the values may be modified on return.
   virtual void VisitPointers(Object** start, Object** end) = 0;
 
+  // Handy shorthand for visiting a single pointer.
+  virtual void VisitPointer(Object** p) { VisitPointers(p, p + 1); }
+
   // To allow lazy clearing of inline caches the visitor has
   // a rich interface for iterating over Code objects..
 
@@ -10368,22 +10371,14 @@ class ObjectVisitor BASE_EMBEDDED {
   // about the code's age.
   virtual void VisitCodeAgeSequence(RelocInfo* rinfo);
 
-  // Handy shorthand for visiting a single pointer.
-  virtual void VisitPointer(Object** p) { VisitPointers(p, p + 1); }
-
   // Visit pointer embedded into a code object.
   virtual void VisitEmbeddedPointer(RelocInfo* rinfo);
 
-  // Visits a contiguous arrays of external references (references to the C++
-  // heap) in the half-open range [start, end). Any or all of the values
-  // may be modified on return.
-  virtual void VisitExternalReferences(Address* start, Address* end) {}
-
+  // Visits an external reference embedded into a code object.
   virtual void VisitExternalReference(RelocInfo* rinfo);
 
-  inline void VisitExternalReference(Address* p) {
-    VisitExternalReferences(p, p + 1);
-  }
+  // Visits an external reference. The value may be modified on return.
+  virtual void VisitExternalReference(Address* p) {}
 
   // Visits a handle that has an embedder-assigned class ID.
   virtual void VisitEmbedderReference(Object** p, uint16_t class_id) {}