Decouple root visitors from object visitors.

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index 82ea67a0a91e2cbac551d0dd6e5c33fe8e600d33..a824771a3235d7f0c0727c982099d8445a474c12 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -50,6 +50,7 @@
 #include "src/tracing/tracing-category-observer.h"
 #include "src/v8.h"
 #include "src/version.h"
+#include "src/visitors.h"
 #include "src/vm-state-inl.h"
 #include "src/wasm/wasm-module.h"
 #include "src/wasm/wasm-objects.h"
@@ -200,8 +201,7 @@ Address Isolate::get_address_from_id(Isolate::AddressId id) {
   return isolate_addresses_[id];
 }
 
-
-char* Isolate::Iterate(ObjectVisitor* v, char* thread_storage) {
+char* Isolate::Iterate(RootVisitor* v, char* thread_storage) {
   ThreadLocalTop* thread = reinterpret_cast<ThreadLocalTop*>(thread_storage);
   Iterate(v, thread);
   return thread_storage + sizeof(ThreadLocalTop);
@@ -213,19 +213,18 @@ void Isolate::IterateThread(ThreadVisitor* v, char* t) {
   v->VisitThread(this, thread);
 }
 
-
-void Isolate::Iterate(ObjectVisitor* v, ThreadLocalTop* thread) {
+void Isolate::Iterate(RootVisitor* v, ThreadLocalTop* thread) {
   // Visit the roots from the top for a given thread.
-  v->VisitPointer(&thread->pending_exception_);
-  v->VisitPointer(&(thread->pending_message_obj_));
-  v->VisitPointer(bit_cast<Object**>(&(thread->context_)));
-  v->VisitPointer(&thread->scheduled_exception_);
+  v->VisitRootPointer(Root::kTop, &thread->pending_exception_);
+  v->VisitRootPointer(Root::kTop, &thread->pending_message_obj_);
+  v->VisitRootPointer(Root::kTop, bit_cast<Object**>(&(thread->context_)));
+  v->VisitRootPointer(Root::kTop, &thread->scheduled_exception_);
 
   for (v8::TryCatch* block = thread->try_catch_handler();
        block != NULL;
        block = block->next_) {
-    v->VisitPointer(bit_cast<Object**>(&(block->exception_)));
-    v->VisitPointer(bit_cast<Object**>(&(block->message_obj_)));
+    v->VisitRootPointer(Root::kTop, bit_cast<Object**>(&(block->exception_)));
+    v->VisitRootPointer(Root::kTop, bit_cast<Object**>(&(block->message_obj_)));
   }
 
   // Iterate over pointers on native execution stack.
@@ -234,14 +233,12 @@ void Isolate::Iterate(ObjectVisitor* v, ThreadLocalTop* thread) {
   }
 }
 
-
-void Isolate::Iterate(ObjectVisitor* v) {
+void Isolate::Iterate(RootVisitor* v) {
   ThreadLocalTop* current_t = thread_local_top();
   Iterate(v, current_t);
 }
 
-
-void Isolate::IterateDeferredHandles(ObjectVisitor* visitor) {
+void Isolate::IterateDeferredHandles(RootVisitor* visitor) {
   for (DeferredHandles* deferred = deferred_handles_head_;
        deferred != NULL;
        deferred = deferred->next_) {