Revert "Eliminate fake-Isolate workaround from concurrent sweeper."

runtime/vm/raw_object.h

Index: runtime/vm/raw_object.h
===================================================================
--- runtime/vm/raw_object.h	(revision 44632)
+++ runtime/vm/raw_object.h	(working copy)
@@ -395,7 +395,6 @@
     return ((GetClassId() == kFreeListElement));
   }
 
-  // Uses the class table of the current isolate, when needed.
   intptr_t Size() const {
     uword tags = ptr()->tags_;
     intptr_t result = SizeTag::decode(tags);
@@ -408,19 +407,6 @@
     return result;
   }
 
-  // Like above, but avoids Thread/Isolate::Current.
-  intptr_t Size(const ClassTable* class_table) const {
-    uword tags = ptr()->tags_;
-    intptr_t result = SizeTag::decode(tags);
-    if (result != 0) {
-      ASSERT(result == SizeFromClass(class_table));
-      return result;
-    }
-    result = SizeFromClass(class_table);
-    ASSERT(result > SizeTag::kMaxSizeTag);
-    return result;
-  }
-
   bool Contains(uword addr) const {
     intptr_t this_size = Size();
     uword this_addr = RawObject::ToAddr(this);
@@ -491,7 +477,6 @@
   }
 
   intptr_t SizeFromClass() const;
-  intptr_t SizeFromClass(const ClassTable* class_table) const;
 
   intptr_t GetClassId() const {
     uword tags = ptr()->tags_;