[proxies] Make Object.prototype.isPrototypeOf work with proxies.

src/runtime/runtime-debug.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
 #include "src/debug/debug.h"
 #include "src/debug/debug-evaluate.h"
 #include "src/debug/debug-frames.h"
@@ skipping 1354 matching lines @@
 
   List<Handle<JSObject> > instances;
   Heap* heap = isolate->heap();
   {
     HeapIterator iterator(heap, HeapIterator::kFilterUnreachable);
     // Get the constructor function for context extension and arguments array.
     Object* arguments_fun = isolate->sloppy_arguments_map()->GetConstructor();
     HeapObject* heap_obj;
     while ((heap_obj = iterator.next())) {
       if (!heap_obj->IsJSObject()) continue;
-      JSObject* obj = JSObject::cast(heap_obj);
+      Handle<JSObject> obj(JSObject::cast(heap_obj));
       if (obj->IsJSContextExtensionObject()) continue;
       if (obj->map()->GetConstructor() == arguments_fun) continue;
       if (!obj->ReferencesObject(*target)) continue;
       // Check filter if supplied. This is normally used to avoid
       // references from mirror objects.
-      if (!filter->IsUndefined() &&
-          obj->HasInPrototypeChain(isolate, *filter)) {
-        continue;
+      if (!filter->IsUndefined()) {
+        Maybe<bool> maybe = Object::HasInPrototypeChain(isolate, obj, filter);

[Toon Verwaest, 2015/12/03 11:29:02]

Debug methods are not supposed to have side-effects.

[Toon Verwaest, 2015/12/03 11:30:32]

Plus we are iterating the heap. Allocating here could be pretty bad.

+        MAYBE_RETURN(maybe, isolate->heap()->exception());
+        if (maybe.FromJust()) continue;
       }
       if (obj->IsJSGlobalObject()) {
-        obj = JSGlobalObject::cast(obj)->global_proxy();
+        obj = handle(JSGlobalObject::cast(*obj)->global_proxy());
       }
       instances.Add(Handle<JSObject>(obj));
       if (instances.length() == max_references) break;
     }
     // Iterate the rest of the heap to satisfy HeapIterator constraints.
     while (iterator.next()) {
     }
   }
 
   Handle<FixedArray> result;
@@ skipping 293 matching lines @@
   return Smi::FromInt(isolate->debug()->is_active());
 }
 
 
 RUNTIME_FUNCTION(Runtime_DebugBreakInOptimizedCode) {
   UNIMPLEMENTED();
   return NULL;
 }
 }  // namespace internal
 }  // namespace v8