Add checks for per thread heap

third_party/WebKit/Source/platform/heap/Heap.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 184 matching lines @@
     static inline bool isHeapObjectAlive(T* object)
     {
         static_assert(sizeof(T), "T must be fully defined");
         // The strongification of collections relies on the fact that once a
         // collection has been strongified, there is no way that it can contain
         // non-live entries, so no entries will be removed. Since you can't set
         // the mark bit on a null pointer, that means that null pointers are
         // always 'alive'.
         if (!object)
             return true;
+        // TODO(keishi): some tests create CrossThreadPersistent on non attached threads.

[keishi, 2016/05/26 04:33:02]

The tests that require this are:
ExtensionApiTest.TabAudible
ScriptStreamingTest.EncodingFromBOM
ScriptStreamingTest.EncodingChanges
ScriptStreamingTest.SuppressingStreaming
ScriptStreamingTest.CompilingStreamedScriptWithParseError
ScriptStreamingTest.ScriptsWithSmallFirstChunk
ScriptStreamingTest.CancellingStreaming
ScriptStreamingTest.CompilingStreamedScript

[haraken, 2016/05/26 07:52:29]

Conceptually it should be valid to support CrossThreadPersistent created on a
not-attached thread, so there is no reason we must fix the TODO. But if it
happens only in testing, I'd prefer fixing the test and removing the TODO (in a
follow up CL).

[keishi, 2016/05/26 11:52:54]

OK. Leaving the TODO comment.

+        if (!ThreadState::current())
+            return true;
+        if (&ThreadState::current()->heap() != &pageFromObject(object)->arena()->getThreadState()->heap())
+            return true;

[haraken, 2016/05/25 15:41:22]

Would you help me understand why we need to add this code? Returning true means
that if a thread calls isHeapObjectAlive(object) for an object that is dead in
another thread's heap, it returns true. I don't fully understand what it
means...?

[keishi, 2016/05/26 04:29:38]

Added this while debugging but it looks like it wasn't necessary. Removed.

         return ObjectAliveTrait<T>::isHeapObjectAlive(object);
     }
     template<typename T>
     static inline bool isHeapObjectAlive(const Member<T>& member)
     {
         return isHeapObjectAlive(member.get());
     }
     template<typename T>
     static inline bool isHeapObjectAlive(const WeakMember<T>& member)
     {
@@ skipping 379 matching lines @@
 void VisitorHelper<Derived>::handleWeakCell(Visitor* self, void* object)
 {
     T** cell = reinterpret_cast<T**>(object);
     if (*cell && !ObjectAliveTrait<T>::isHeapObjectAlive(*cell))
         *cell = nullptr;
 }
 
 } // namespace blink
 
 #endif // Heap_h