Introduce a PrototypeIterator template and use it all over the place

src/ic.cc

Index: src/ic.cc
diff --git a/src/ic.cc b/src/ic.cc
index cd92af11852c0f77c7140804cf6500e767087474..c46e831dfa419c9133de9b36fb32ce07ba56f3e0 100644
--- a/src/ic.cc
+++ b/src/ic.cc
@@ -11,6 +11,7 @@
 #include "src/conversions.h"
 #include "src/execution.h"
 #include "src/ic-inl.h"
+#include "src/prototype-iterator.h"
 #include "src/runtime.h"
 #include "src/stub-cache.h"
 
@@ -213,7 +214,7 @@ static void LookupForRead(Handle<Object> object,
       return;
     }
 
-    Handle<Object> proto(holder->GetPrototype(), lookup->isolate());
+    Handle<Object> proto(SAFE_GET_PROTOTYPE_FAST(*holder), lookup->isolate());
     if (proto->IsNull()) {
       ASSERT(!lookup->IsFound());
       return;
@@ -239,7 +240,7 @@ bool IC::TryRemoveInvalidPrototypeDependentStub(Handle<Object> receiver,
       break;
     case PROTOTYPE_MAP:
       // IC::GetCodeCacheHolder is not applicable.
-      if (receiver->GetPrototype(isolate())->IsNull()) return false;
+      if (SAFE_GET_PROTOTYPE(isolate(), *receiver)->IsNull()) return false;
       break;
   }
 
@@ -1210,7 +1211,7 @@ static bool LookupForWrite(Handle<JSObject> receiver,
     // goes into the runtime if access checks are needed, so this is always
     // safe.
     if (receiver->IsJSGlobalProxy()) {
-      return lookup->holder() == receiver->GetPrototype();
+      return lookup->holder() == SAFE_GET_PROTOTYPE_FAST(*receiver);
     }
     // Currently normal holders in the prototype chain are not supported. They
     // would require a runtime positive lookup and verification that the details
@@ -1438,7 +1439,7 @@ Handle<Code> StoreIC::CompileHandler(LookupResult* lookup,
           // from the property cell. So the property must be directly on the
           // global object.
           Handle<GlobalObject> global = receiver->IsJSGlobalProxy()
-              ? handle(GlobalObject::cast(receiver->GetPrototype()))
+              ? handle(GlobalObject::cast(SAFE_GET_PROTOTYPE_FAST(*receiver)))
               : Handle<GlobalObject>::cast(receiver);
           Handle<PropertyCell> cell(global->GetPropertyCell(lookup), isolate());
           Handle<HeapType> union_type = PropertyCell::UpdatedType(cell, value);