VM: Const-correctness fixes.

runtime/vm/raw_object.cc

Index: runtime/vm/raw_object.cc
diff --git a/runtime/vm/raw_object.cc b/runtime/vm/raw_object.cc
index 74013a6d5474f84e74143baf56aa710b0022a27f..ba53d37e4761b6fd03ec9b4e167dbda8a08a5dfd 100644
--- a/runtime/vm/raw_object.cc
+++ b/runtime/vm/raw_object.cc
@@ -165,7 +165,7 @@ intptr_t RawObject::SizeFromClass() const {
       break;
     }
     case kFreeListElement: {
-      uword addr = RawObject::ToAddr(const_cast<RawObject*>(this));
+      uword addr = RawObject::ToAddr(this);
       FreeListElement* element = reinterpret_cast<FreeListElement*>(addr);
       instance_size = element->Size();
       break;
@@ -277,7 +277,7 @@ intptr_t RawObject::VisitPointers(ObjectPointerVisitor* visitor) {
       }
 #undef RAW_VISITPOINTERS
       case kFreeListElement: {
-        uword addr = RawObject::ToAddr(const_cast<RawObject*>(this));
+        uword addr = RawObject::ToAddr(this);
         FreeListElement* element = reinterpret_cast<FreeListElement*>(addr);
         size = element->Size();
         break;
@@ -303,7 +303,7 @@ intptr_t RawObject::VisitPointers(ObjectPointerVisitor* visitor) {
 
 bool RawObject::FindObject(FindObjectVisitor* visitor) {
   ASSERT(visitor != NULL);
-  return visitor->FindObject(const_cast<RawObject*>(this));
+  return visitor->FindObject(this);
 }